If I understand you correctly, you are saying that taboos should not be examined from within the space where they hold effect, because doing so calls into question the whole concept of a taboo and robs all taboos of their usefulness, and that would summon evidence for, or even cause cultural decline?

That sounds suspiciously like something a taboo would say that has something to fear from being looked at. ;)

I think this chain of reasoning is made of links that do not self-evidently follow. From my lay perspective, taboos seem more complex, resilient and variable to require a perfectly dogmatic approach to hold up. If they were this easy to bring down, they'd all be gone.

I'm also not sure what a "culture without taboos" is, or one has ever existed. Also, what is meant by "peak"? Is there an optimal amount or set of taboos? How do cultures with taboo-ical differences (and their peaks) compare to each other across space and time?

I think it is good and healthy to approach taboos with curiosity, whether it is to interrogate them or to appreciate them more.