RMS has always been an impractical idealist. However, things that were considered his feverish dreams are now mainstream. To be able to move forward, there must be people advocating for an ideal world or we will stop approaching it.
While the proportion of GNU code in a modern Linux distribution is not what it was before, still in each Ubuntu or Fedora or even Android, there is far more GNU than Linux. There is a bunch of competing projects that sometimes reduce that, but it is very important to never forget where we came from. The whole closed source saga was posiible, because early programmers simply did not understand the values and global benefits of software freedom that they then had. We must never forget the lessons of software history or we shall be doomed to repeat it.