Changes happen in every sport not just NASCAR. The NFL, MLB, NBA, and NHL have all changed since the 80s-90s.
NFL has changed what a catch is, took out horse collar tackles, made the Brady rule to protect The QBs, the tuck rule, made changes to kickoffs and extra points among others.
MLB has taken out ho.e plate collisions, added playoff teams, introduced instant replay, and made the all star game count for something.
NHL has introduced shootouts, the Avery Rule, and reduced the goalie padding.
NBA, soccer, golf, tennis, college sports have all made changes over the last 20 years.