For starters it was much more difficult to get lewd and even safe pics since internet and anime weren't as popular as they are now. There also was a bigger presence of western pics and characters because they were easier to get and understand compared to Asian stuff.
Shotas also were much different before. Before the "cute boyish" aesthetic of today shotas were either miniature men (with proportions that didn't match the implied age at all) or miniature flat-chested girls with a penis (again with mismatching proportions). In case of western works, the shotas were either ugly aged up versions of a character or "regular-sized" but with huge adult cocks attached to them.
Regarding fetishes, most pics/comics/doujins were /ss/ involving incest or cheating, and the few gay ones usually had rape scenes because artists were more sadistic at that time.
Honestly, I personally thank Mitsui Jun for breaking all of these garbage tropes with his doujins and paving the way for a new and more adorable iteration of shotas. Instead of drawing manlets or mini dickgirls he drew actual boys with cute little bodies that make you want to hug them, and the darker premises of the past were replaced with lewd but innocent stories. I also should thank 4chan and similar forums because they helped to spread the "otaku" culture around internet (and shotacon as a consequence of it).