There is still a lot of content(raids/dungeons) outside of BFA and Shadowlands that is fun and engaging to play in a group setting. I understand you can always solo old content but myself and many others enjoy the social aspect of MMOs. All this level squish and "rush to endgame" has done is make most of the pre BFA content obsolete and makes it harder to find people who want to play it. It feels too separated now, there's everything before level 50 (which has been made mostly solo) and then there's everything after 50.