If you choose to define 'meditation' as 'sitting quietly and thinking [perhaps with a side order of deep breathing], I would say that Terence is, frankly, full of shit. While psychedelics may indeed offer far more in the way of 'religious experience,' I doubt highly that a person with an IQ of 80 who took daily doses of Ayahuasca would come to any deep conclusions regarding the certainty of their mortality when compared to someone with an IQ of 180 who mostly sat around and thought a lot. And for what it's worth, I've found the latter to be a considerably healthier way to achieve personal understanding, at least in the long run. My own conceptions of 'meditation' aside, Terence McKenna did devote a humorous portion of his lectures to contrasting so-called 'practitioners' or 'yogis' who would repeatedly inform him that he was just "doing it wrong" with shamans who guide initiates on 'vision quests' in which any notion of "doing it wrong" is basically irrelevant.
I mention my own understanding of what meditation actually is because I would like to ask the following: Why must all wisdom regarding the human condition be delivered by a such a (naturally) rare, climactic, and highly volatile form of psychic upheaval as a psychedelic or 'religious' experience? That is, why must one arrive at spiritual knowledge solely by means of violent alterations of consciousness as opposed to simply thinking and reading a lot about ideas that intrigue or compel them? If you find yourself believing wholeheartedly that the answers to all or most of your big cosmic questions will be delivered by means of some psychedelic potion or a deep breathing session, I strongly suggest that you reevaluate what exactly it is that you intend to gain from such pursuits.