This is the reason why I implemented rather dumb but individual, hand-crafted captchas for my own websites in the past. Things like input fields which must be left empty, silly multiple choice questions only humans could properly answer at that time, etc.

I have seen communities to implement their own captchas with domain knowledge. For instance, math/STEM people showing captchas with rather easy calculus tasks (such as solving a definite integral). This can be fun to solve and as a human you feel valued. It is this handmade feeling of the "old internet".

The problem with self-made captchas is that even them are rather easy to solve nowadays with LLMs and thelike. Therefore I don't believe that decentralized individualized captchas are the solution as they tend to be rather simple.