Anime wasn't that popular outside Japan so they didn't try to appeal to everyone , the stories and characters had more depth in older animes while allot of new animes are fast paced and focus more on animation less depth and are generally very short , what i noticed too is some genres died or are fading away slowly like idols , racing , mecha in favor of other genres like shonen action isekai.
i remember watching Megazone23 ova during pandemic and i was blown away from how good the characters and story and animation are for the 80's.... we are not having ova or movies like that anymore now