If it's part of a critique, that's fine, that's one thing--but if it's a professional artist who you don't know or didn't ask--that's totally different.
Most professional art has a lot of influence by non-artist comittees, and they don't get to have full say in what goes down in the final product. To call them a bad artist because of something they may have no control over (I mean look what happened to Sonic) is a complete misunderstanding of how the business works. That, and I think the whole "correcting" thing pushes more and more that only one or two art styles are "good" while the rest can just rot.
Remember that what may look good on instagram or on twitter, is actually maybe not good for the original product (especially when people do Photoshops of 3d characters--yo, you have to rig and animate those characters--do you have any idea how those are made? they don't make them in Photoshop. 3D characters are made to be animated, and that rigging is a PAIN in the ass.)
I do think it's OK to direct criticism at a company when that happens if there's something really wrong (again, like for sonic), but you have to be careful because if you do these "corrections" it can make the original artists look really bad in their managers eyes--it could potentially lose them future jobs for, again, something they may not have had any control over in the first place.
Like it's hard to explain unless you've had that client--but the worst thing ever, is when you finally finish a job to a client's wishes, and then they love it, and then they show it to a friend or someone random comes over and mentions "oh, but maybe it should be this way instead?" And GUESS WHAT, 100% of the time, you will be asked to redo everything because one of one random guy who has no idea what he's talking about. Don't be that random guy.
If you do decide to "redo" something, make it in the spirit of appreciating the thing. Like when people "redid" anime screenshots for a meme a while back, it was a celebration of the anime, not a criticism. There's a right way and a wrong way.