Why are 'less' and 'fewer' not being used correctly anymore? Is it not taught in school nowadays? And why does 'much' and 'many' not seem to have the same issue?

I keep seeing everyone using 'less' for everything even when it is incorrect, e.g. 'less people'. Is 'fewer' being phased out of English grammar in schools or is this a social change in the language being people are not learning 'correct' English?

Is this the same issue that is happening with 'good' vs 'well'?