The thing about only having one data point for life in the universe is that the "Goldilocks Zone" only describes planets that have ideal conditions to support Earth-like life. Who's to say that Earth-like life is the only form of life that exists or is possible? I think we assume too much.
I disagree. We understand enough about the universe to understand that life as we know it, which I'll explain in more depth in a moment. Can only exist within certain parameters. Having an upper and lower limit on temperature. Among other things.
Now I say life as we know it, because life as we can't conceive of its a pointless thing to consider. Anything becomes possible when you do away with all reason and logic and just go with an infinite number of "but what if"s.
For example, life can't exist below a certain temperature because at such temperatures the energy needed for life to function doesn't exist. It doesn't work above certain temperatures because all life as we can conceive it, and again going beyond that is pointless conjecture the likes of which make sensible discussion impossible. Because life requires genetic code and genetic code requires that the molecules that contain the code don't get destroyed by heat breaking their bonds.
We can safely safe within the realm of sensible thought that life exists within certain parameters. It may not require oxygen, it may not require liquid water, although we do for it to support our kind of life. But there are limits to sensible possibilities.
What a lot of people think are just scientists making assumptions are actually that the scientists grasp the underlying mechanics of it all a lot better.
As for intelligent life, that gets a lot harder.
People also fail to consider that it's no accident that life in earth's works like it does, that it's not chance. Like when people suggest the possibility of silicon based life. Carbon isn't the building block of all known life by accident. It is because it is the ideal element to build the complex molecules genetic code requires. Nothing else is as ideal. There are other elements that are close like silicon and sulfer. Relatively close anyway. But odds are all or almost all life in the universe is carbon based.
Once you get to a certain point, it ceases to be open mindedness and becomes mindless conjecture. If you expand the "what ifs" beyond a certain point, sensible discussion becomes impossible because other concepts that make useful acedemic discussion impossible also start coming into the picture.
So you start with things like "what about life that doesn't use anything like rna or DNA" and quickly it can just as well devolve into "well what if all of reality exists as a dream we are having and you and you alone are the only sentient creature in existence, a God unto yourself". "well what if the periodic table and all known science is an elaborate hoax". If you can't accept some things as likely enough to be true to just do away with doubt, it can quickly become so abstract that nothing of use gets pondered or accomplished whatsoever.
And within what we know well enough to say it's as certain as it gets we can safely say we know life has certain limits. There is almost certainly other life in the universe and in our galaxy, it is likely carbon based and it likely exists almost exclusively on planets similar to earth. It's likely almost all or entirely all carbon based and most of it likely requires liquid water or at least another similar liquid solvent if it's biochemistry can be different. Which is a decent sized if to start with without going way further into speculation.
Science isn't about knowing things for certain. It's about going with the most likely to be correct answers until something better comes along. And in the spirit of that, acting on any conjecture or speculation that is totally unsupported by any of the information that has shown itself repeatedly to be reliable in searching for or considering life beyond the sensible parameters would be unscientific and a waste of precious resources.
I truly hope that in my lifetime we are able to really see planets in other star systems. The potential for what is out there in the at-least-nearly-infinite universe has to be the most fascinating thing to me, it's always been that way. I would love SO MUCH to be able to see what life on another planet looks like, any form of life, though of course other intelligent life would be the most interesting. Or to visit... what a trip that would be (figuratively and literally 
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