In my opinion, SL has to offer what all the other expansions had to offer.
PvP - Raiding - Dungeons.
It's never been different. M+ is still fun and challenging.
The raid is fun.
I don't play PvP but I guess it's been an improvement, at least when we are talking about rewards etc.
"Open world" has always been completely pointless from TBC onwards to this day.
Nothing new in WoW.
It's a working formular and that's about it.
I'd rather have them drown me in cosmetic rewards, optional spell animations (like glyphs that change the colour/style of your abilities), challenge mode dungeons (on top of M+) that reward players with a new set etc.
But all of that would be "I did it once and never touch it again" - I don't think it's possible for Blizzard to get me to play more than once or twice a week anymore after the initial rush. I wouldn't know how - at least not with realistic expectations in mind.
All the fun stuff I usually like is often disliked by the community.
Grinding Legendaries, grinding Artifact weapons, Warforge/Titanforged gear etc. etc.
People always look at this shit from a competitive side like the baboons they are. "I don't want this person to have the same gear as me" or "I don't want someone else to be ahead of me".
Since that mindset never changed, there has been no real content whatsoever once you are at a certain gear level for basically a decade.
No way to improve your stats.. or to increase your powerlevel, nothing to unlock to make your character stronger after spending some hours grinding something.
So the only other thing that would engage me are the one-time challenging stuff, but that's something Blizzard won't do because that stuff is not worth it for Blizzard to put money/work into, since it's a one-time thing that can't be re-used to occupy players for X months.