It’s not a recent thing, but I would say there has been a decline over the last decade or so. Not only does it seem like spelling and grammar are getting worse but I feel it is much more likely these days to find comments defending improper English rather than correcting it.

I saw someone spell “extreme” as “extream” which is just kind of baffling, I actually can’t even imagine how one would make such a mistake?

Maybe they had just come from dealing with large quantities of paper? Or enlarging a bunch of holes?