It's long-established in its usage and while you can call it a 'regionalism', it's accepted in numerous regions with significant geographic and cultural distance.

If you aren't the kind of person who kvetches about "ain't", or kvetch, for that matter, don't kvetch about positive anymore.

I do pilates anymore [<- doesn’t work, you want “still do pilates” or “still do pilates these days” or something]

"I do pilates anymore" would be saying that I didn't do pilates before, but I am now. So 'still' would make the sentence express the opposite of what it's trying to.

It always rains in the winter anymore [<- doesn’t work because it’s describing something common]

It works because it didn't used to rain in the winter all the goddamn time. Climate change has caused weather patterns to change, so if someone says "It always rains in the winter anymore", that is saying that it used to snow in the winter (implicitly when what they remember they were young rather than speaking from a statistical analysis), but now it always rains instead.