After a month of playing now, with the initial impression being overall good, SL now feels like it is there just to keep people busy for the sake of being busy at this point. So far, it's been neither a "journey of fun and wonders" nor exploration nor a search for powerful loot or cosmetics to be felt. Just feels like the objective from the beginning was logging in to check out what they came up with for dungeons and systems this time around and how the gated content is done differently from last time using renown, which makes it feel more like a progression in a way. The story feels weak and unexciting.
The zones and overall story after being seen once only makes up 10% of SL for me, the remaining 90% is just a boring grind that feels too familiar and unrewarding. Still hopeful that this gets taken care of in 9.1+. Flying is a must for the "exploration part". It's enough to grind this far and see it all on the ground. Also would have been nice if they made the intro quest skippable for alts, but it is too late, I am fully burned out because of it and I feel like it is time to take a break for a while.
If there was one thing I wish to see in WoW that is not far fetched or unreasonable, that would be: having mini dungeons made up of previous expansion raids playable as timewalking instances from 50->60 as a choice after clearing SL leveling content once for variety's sake as opposed to the repetition of the same 3-4 things over and over. 10->50 is so much more fun than 50->60 regardless of how many times you do it due to the massive selection of dungeons and many expansions as available choices to spice things up. Anyway, the new SL dungeons will get played endlessly in heroic/mythic/m+ and this suggestion is not for M+, but for leveling only.
It's not because you've done it all that it starts to feel boring, I have only done 20 to 30 percent of SL so far. I'm just not interested in SL as much as I am in the non SL WoW content. It is very important to create new content in light of older content and make sure it stands out in a good way compared to previous content otherwise it will fail and disappoint. At the same time, old content must not be ignored and rendered irrelevant which is currently the case for raids only (compared to leveling dungeons/different expansion questing).
I don't login to do some weeklies or daily, but to actually try and learn a new spec while enjoying a dungeon or an LFR raid. My choices are currently severely limited because I am stuck with current content only at level 51+ on all my alts.
I don't think this is something that should be addressed via a korrak's revenge or invasions or something short term and for SL only, but via a long term solution that never gets old and the only thing that comes to mind is turning old raids into dungeons for levels 50 to 59 after clearing all current content first on a single character.
Ton of variety, fun and challenge while waiting for gating BS to get taken care of in future patches. A great example of this solution is the anniversary multi raid boss event.