Since Drupal 8, there has been a mostly smooth migration path between major versions, so you can upgrade from 8 to 9 to 10 relatively easily.
One bump in the road can be the availability of modules for the new version. Drupal 8 and 9 were only supported for a year after the release of their successors, which didn’t help. While quite a lot of modules had a release supporting the next version quickly, there seemed to be quite a few that were very slow to update, and quite a few sites were waiting for one or two modules to release compatible versions before being able to upgrade. I think there are…