One can draw opinions from first principles reasoning sure.

Conclusions, no. Especially if the data does not agree with your reasoning. Which is almost always the case for unknown unknowns.

What first principles reasoning (by experts on a topic) is genuinely useful for is to prioritize what to pursue/research next.

First principles reasoning by amateurs gets you results that are 'not even wrong'.

https://en.wikipedia.org/wiki/Not_even_wrong