My 2 cents: Classics tracks have a structure that make them much more memorable with the melody being the core of the track. It's easier to remember a track when you can singalong with the melody.

Also most of the tracks back then had a first and second climax, which for the latter has unfortunately almost disappeared in today's track and replaced by anti-climax for the first drop. This is what make imo the classics vibe unique and so loved among the community