Just because Drupal core is supported, it doesn’t mean that all of the other modules your project uses are still also supported or actively worked on.
Since the Drupal 8 release in 2015, I’ve seen numerous examples of modules that haven’t been updated for some time as maintainers focus on writing and maintaining the versions for Drupal 8 and now 9 and 10.
Whilst it isn’t marked as unsupported, it isn’t being updated either.
I recently explained to a client that their site uses a module last released in 2014. It’s buggy, but there’s no newer version to use and issues in the queue are no longer being fixed or triaged.
Override Node Options - a popular module I maintain - is in a similar situation. The most recent Drupal 9/10 version was in February 2023, whereas the last Drupal 7 release was in March 2018.
I don’t have any official figures to support this, but feel the contribution rate for Drupal 7 projects (as in modules, themes and distributions) has been slowing for some time.
Meanwhile, Drupal 7 core is still supported, at least for now.