IMO, so this is most likely of no value to anyone, i think the only thing of SL that is an abject failure, is the story, full stop. The community has spoken, and no one is enjoying this dumpster fire of a story. Now we can have a long discussion about what parts are bad, and what parts are good, but that would be a whole other topic.
But with out a doubt, the community, at large thinks the story is the big doo doo.
That said i think SL is also the victim of circumstance. SL did have a great launch, but got hit hard with all the delays and lock downs that the entire schedule got messed up. I think if korthia would have been about 2 months earlier we would be in a far better place.
That said i dont think SL is free of all blame, i think they made some bad choices along the way. Namely locking covenets to 1 per player and screwing you out of it hard core.
Locking story and content like that is a massive shame, and setting your self up for failure, many people dont do multiple toons, so you are having massive swaths of content being missed out my a lot of players.