FWIW, I still use `interactive-p' in much of my code, because the code
needs to work also with older Emacs versions.  And because I have never
noticed any problem, for this code anyway, with `interactive-p'.

What's more, the doc for `interactive-p' does not really tell you how
to replace it - it just says to use `called-interactively-p', without
any mention of which argument gives you the behavior you had previously
with `interactive-p' or similar-but-somehow-improved behavior.

`interactive-p' was indeed used heavily, over decades.  And it is no
doubt still in use quite a bit.  Too bad there is next-to-no guidance
on how to use `called-interactively-p' to replace it.