I actually have to disagree with you on this point. I actually had lots more fun with the old content. Raids and Dungeons were always available, had cooler gear and I resigned myself to not getting any of it as I did neither and my game play did not suffer for it. I had content and more importantly, story to entertain me and be ‘in character’ as it were and so enjoy the game.
The problem with the later expansions is that you are forced to do dungeons and possibly raids to progress in the story and the game. Given the pressure of being ‘good’ in a dungeon (and if you’ve done solo PvE you’ve NO experience and no way to get any) it’s more likely than not going to be a less than stellar experience.
The focus has been more and more on endgame rather than play in general. I recently created a worgen on a server and I have to say the initial intro-storyline was delightful. You could feel involved, in character and the story progressed and more importantly, I found it fun.
Shadowlands has so many systems that you must grind (and fewer quests/options than BFA had) it gets repetitive, boring and what little story there is becomes quickly lost.
I’m not saying not to have dungeons and raids. If I had the time to invest, I would enjoy them, but I don’t. The success with WoW in the past is that it had something for everyone.
Shadowlands has the feel of something for a subset of everyone with a nod to the rest.
I’m not sure the suggestions made to improve things are viable, but the time sink as well as the reward for time are definitely valid points.