From my observations, deviantart now is... just full of perv shit, kinks and art of some specific fandoms (and often all three at once).
I wasn't ever posting my art on dA that much - I was always mostly a lurker - but my newest account, which I kinda gave up on because just can't be bothered to post there, has like... 8 watchers? lol (and that's after posting everything to a bunch of groups) And now that there's the terrible eclipse layout which I just can't get used to, I feel like going on dA even less.
I mostly use pixiv as a gallery for my art, but I can see how the site isn't appealing for those who don't draw anime-styled works or anything anime-related, and it has its share of creepy pervs too. (Though, the kink shit is nowhere as prominent as on dA - prob because pixiv just has more of everything so the weird fetishes get drowned out.) Artstation is... hahahah, WAY too intimidating for a mediocre self-taught artist such as me.
I do post on twitter and tumblr but they're not optimal as a gallery, for reasons mentioned in many posts above, and it's really hard to get any traffic on twitter for me.
Honestly, imo the internet as it is now really sucks for artists... and just sucks in general. I so wish it could be turned back to how it was a decade ago, before twitter, instagram and facebook devoured everything else.