How is it that animation from the 80's still looks good to this day? Always loved Rumiko's designs and Lum still looks good even today

Every generation before yours was not randomly and needlessly incompetent; weird but true. (And a lesson that we have to constantly try and fail to learn.)

No really, EVERY. SINGLE. TIME. We've still got people who will believe that aliens decided to make a random desert civilisation and then leave before they'll believe that people thousands of years ago somehow WEREN'T so fundamentally inferior to us that making a large triangular building would be beyond them.

80s animation looks good because people who were good animators happened to live in the 80s.