Am I just being overly pessimistic? Has the internet jaded me?
Yes and yes.
The average person is a piece of shit. Vain, greedy, selfish and self centered. I am not religious, but the 7 deadly sins are the normal human condition.
True altruism is rare and not the norm for humans. True love is also rare. A person which has shed all of the negative human traits is nearly non existent.
With what metric are you measuring these things?
Everyone has the capacity to be vain, greedy, selfish, etc, for sure. But everyone also has the capacity to be selfless and compassionate and to embody the opposite quality of whatever the 7 deadly sins are. Both things are part of the human condition. It doesn't make sense to say that the average person is mostly just shit, ie, embodying mostly just the negative side. Firstly, how can you possibly know this, there are over 8 billion people on the planet but a disconcertingly vast proportion of power and control over the planet's resources that is enabled by wealth is possessed by a comparatively tiny number of people. Unfortunately it is the nature of the current state of affairs that those who are willing to prioritise their own self interest above morality immediately have an edge over those whose actions are constrained by morality, thus effectively rendering the vast majority the human population relatively powerless, voiceless, and unseen. Maybe they are mostly pieces of shit by any reasonable metric but this is just impossible to know, and I would argue unlikely. If you looked only at the loudest and most visible people in the world, I can understand why you might come to this conclusion, but this is an extremely skewed and relatively miniscule segment of the entire human population that is almost guaranteed to be weighted towards those with flexible ethics, so to speak.
True altruism and true love are rare, again, how can you know?
Isn't the fact that we have defined certain qualities as "sins", itself some kind of indicator of an intrinsic ethical framework of some sort? If this were the norm then we would not have defined these things as sins, they would just be normal behaviour. That is, unless you think your own definition of sinfulness, or what it is to be a piece of shit, is significantly different to the norm - although in that case I would caution you to remember the phrase, "if you think it's everyone else who's the problem..."
Consider this - how likely is it on any given day that you will be able to avoid people who are truly pieces of shit? How many people are there around you on any given day who are truly malicious enough to actually interfere with your life, directly? I'm asking because if you live in a part of the world where you have reliable internet access, presumably reliable electricity, access to clean water, and a roof over your head, I think it's likely quite possible that you live in a society that is cohesive enough and stable enough and where there has been a sufficient level of organisation and cooperation between individual human beings over a long enough time period to create these things - which would simply not be possible without a significant degree of mutual trust, respect, cooperation and selfless behaviour - bearing in mind that the corruption and exploitation of labour by unchecked, runaway capitalism is a relatively recent phenomenon over the entire history of our species - that you probably are not in that much actual danger from people who truly are evil, courtesy of the social structures established by people who care about such things as social stability, safety, and their fellow human beings. I would say therefore that it doesn't make much sense to say that most people are just shit, even in the tiny section of society immediately around you, disregarding the roughly 8 billion other unknowns.
If you are conditioned to look for it - or even if not - you can of course easily find examples of the worst examples of human, because these people, as you say, are often loud, and visible. But they are visible, and their presence striking enough that people are inclined to stare at them (virtually, metaphorically), and that people find them entertaining, such that their presence in media and the popular consciousness is disproportionately high compared to their actual number, precisely because these people are outliers, they are entertaining because the magnitude of their sins is striking, baffling, and very much
not the norm even for those people who do actively spend most of their time looking for such people. On the other hand it is the nature of people who embody the opposite ideals that they will be quieter, more humble, they won't brag about their achievements. Because of this it is
more effort to look for these people, and it takes
more cognitive effort to recognise and appreciate them than it does the relatively simple, brash, entertainment appeal of whatever billionaire asshole you can think of. Indeed, antagonistic actions that upset social cohesion are in some ways just
intrinsically more entertaining to watch, as long as they aren't happening to you directly, I guess, than quiet acts of philanthropy that help human society continue to operate more smoothly with less drama. These things are natural instincts which humans are not to blame for, we are primed to recognise disruption and danger more than we are to recognise or appreciate stability, this seems to have been evolutionarily necessary. But of course, the speed with which unprecedented new forms of audiovisual, multisensory entertainment has developed, coupled with the means to distribute this, and the immense inertia of emergent market forces that prioritise accumulation of capital above all else, has changed our environment faster than we have been able to properly adapt to it so far, leading to a complete exploitation of this basic, danger-seeking instinct which means that frankly it is profitable to show us the worst examples of human nature more than it is to show us the best.
An obvious example that I hope no one is cynical enough to both read all that and find controversial is the coverage that Bill Gates gets compared to Elon Musk. Consider the amount of philanthropy that the former has been involved in - and then consider how much people are interested in this, compared to the idea that he might be using 5G to transmit new forms of COVID or something. And then obviously you just have to think about the behaviour of the "fanbase" (ugh) of either individual. I mean... I don't think I need to explain this even.
Do we even deserve to exist?
Strange question, pretty meaningless, honestly. Can you think of even just one person in your life, or one person you can think of in history (although I hope you can think of someone in your life) that you consider to be a genuinely good person, that you have an uncomplicated relationship with. Do you think they don't deserve to exist?
More bluntly, do you think that the fact that you are aware of the potential for evil that exists within humanity is enough to condemn every other good individual to nonexistence? Does it really even make sense to you to ask that question, as if "we" are all a single entity, and responsible by mere virtue of being human for all the worst evils committed by humanity?
Or is evil a natural element of survival and life itself?
Evil is a human concept, and requires a moral framework to mean anything. Is a cat evil when it tortures a mouse to death?
I always end up bringing up this example when faced with this kind of cynicism but it remains one of the best examples I can think of. While we might be the most capable species on the planet, and unarguably technologically superior, we are NOT the most sadistic or violent hominid. Indeed our closest relative, the chimpanzee, is by nature far more brutal, violent and sadistic than we are, they are both smart enough to understand how to hurt each other, and malicious enough to use this knowledge such that when settling disputes with conflict and at least a few deaths, as is, pretty much, the norm, they will have no qualms about breaking and biting fingers, gauging out eyes, and ripping off the balls of their enemies. Are chimpanzees more or less evil than us? Does it even make sense to think in this way about them? Doesn't the fact that we HAVE enough empathy that is seemingly intrinsic, that there is no evidence this was EVER normal human behaviour even in days before any kind of formalised thinking about ethics and morally, despite the fact that we surely have an even greater appreciation for how much this would hurt - mean something?
Of course, there have been sadistic and evil individuals who have exploited this knowledge - but they remain individuals, this kind of evil is exceptional and noticeably abhorrent precisely because it is rare. It is easy for most of us to tell that it is wrong.