To me, there are two main trends in the changing aesthetic of D&D:
1. The move towards Digital Art.
2. The move away from representing only Medieval European Fantasy.
Otherwise, I think D&D art has always had a huge variety of styles. I mean, check out Erol Otus:
View attachment 154074
That's 1981!
When I look at something like this, from the 2e DMG:
View attachment 154075
It doesn't look that much different than these pieces from Radiant Citadel:
View attachment 154076
View attachment 154077
The only kind of art I'm not a huge fan of is one with "photorealistic" people / scantily-clad people from the 2e Era (like this):
View attachment 154078
I much prefer my art imaginative or grungy, like this dwarf artificer from Tasha's:
View attachment 154079
or DiTerlizzi, the D&D artist of my heart:
View attachment 154080