The worst that can be said of older art: it was often boring.
And some of it was anatomically bad:
But today's stuff is often ridiculously over the top:
If I had to pick, I'd say that the early '70s--especially the Marvel books--was an amazing period of comics art. Here's what was being done in 1972, for example:
Gil Kane and John Romita on ASM
Ross Andru on Marvel Team-Up
Sal Buscema on Captain America and Defenders
John Buscema on Fantastic Four and Thor
Neal Adams on Avengers
Gene Colan on Sub-Mariner, DD, and Tomb of Dracula
George Tuska on Iron Man and Luke Cage
Dick Ayers on Sgt. Fury
Gil Kane on Warlock, Kazar, and Marvel Team-Up
Just an amazing list.