Well, even our old friend, innit, has been around in print for half a century, Segilla - first recorded as such in 1959 - so it doesn't look as if it's going away any time soon for the people you refer to in your second paragraph above.
As regards less/fewer, what about "My workplace is fewer than two miles from home, so it takes a taxi fewer than ten minutes to get me there and the driver charges fewer than four pounds." Would anyone say that? I suspect not, yet miles, minutes and pounds are all countable nouns.
There simply are situations - such as the above - which demand the colloquial/idiomatic �less' rather than the - supposedly - correct �fewer'. (The latter became �correct' only in the 18th century in any case. Prior to that, many writers used �less' where purists or pedants now demand �fewer'.) Even English examiners have been known to produce the instruction: "Write a pr�cis of this passage in 50 words or less", never mind the supermarkets with their till-signs saying: "Ten items or less"!
As time passes, we'll see and hear much more of �less' and much less of �fewer', you may count on it! The process is well under way. As an old-timer, I still differentiate between them, but I don't complain about people who choose not to... or don't even know that they �should'.
Whether direct or indirect, language evolution is unstoppable, as you acknowledge. Consequently, I can't see the point in getting annoyed at what is beyond prevention. Cheers