People typically use Tumblr at this point. It's not designed for art, and it has issues with big images, but it has a fairly active community, so people use it. There's also niche sites, like FA for furries and various boorus for anime fans. There's also a semi-active twitter artist community, although 90% of those people also post elsewhere.

Shameless plug: I've been stealth-working on an art site for several years, so you could try that out if you'd like. That's at https://www.imagehex.com/.