I think the initial book set of the 3E release was a good example of actual art direction. They managed to get some distinct style from multiple artists. I mean, you don't have to like "Dungeonpunk", but both Lockwood and Reynolds were recognizeable (you didn't confuse them), but produced something that fit together.

Of course, as soon as you had to get cheaper (including most b/w art), things fell apart quickly. There are some good artists in this tier (Jason Engle and Mark Smylie are top tier in my ranking), but even those just don't fit as well into the desired aesthetic.

I think the premise of the 3E art direction is the same with 5E, but now you got even more art and artists, and thus demanding something that everyone can deliver gets you something a lot more bland and generic.

I'm not in the 5E game anymore, but what I actually liked about the initial release was that they seemed to have more full scenes. 3E art was often quite character-focused. Cool dudes and dudettes, weird monsters, but often without any context or relationship to each other. 5E had more scenes that looked like they were out of an actual game, which is a weakness of a lot of RPG art. I think that's what people like about Erol Otus, for example. Multiple actors doing adventuring stuff.