I get the feeling that the anime you'd categorize as "older" is mostly from before 2000. Or rather, from around the time that art style, animation quality and resolution gave off that feel of not so much being "old", but rather just "not modern"
@Anony_mous I'm definitely with the person that asked that question. They seem pretty old to me. Anything from the early 90s or earlier is ancient in anime years. Then you've got various buried layers of fossils and stuff along the way towards the primordial goo in the 60s or so.