I had a good time with the campaign (and thought it was a great choice to anchor the story around Kamala Khan rather than the 'big name' Avengers from the movies), but after finishing that up, I didn't feel much motivation in engaging with the 'endgame' content for more than an hour or so. I enjoyed the game's combat, and felt most of the characters were decently fun to play as, but there was just something about doing missions to collect for loot which didn't appeal to me much.
It's interesting to some degree, as I feel if the game primarily focused on the single player campaign, I suspect it would have been better received at launch. But with the decision to make this a live service game, the focus of course shifts into 'endgame' content and active players bases after launch.
I'm not sure if live service necessarily is the wrong choice for a game like this in and of itself. The Marvel Universe certainly has enough heroes, villains, and lore to support a continuously updating story and associated content. To me, it's more an issue of execution. I feel live service games require a fairly steady content drip to stay relevant and compete with other live service games. There are so many games to play these days, and if a live service game is going long stretches of time without releasing significant content, it's easy to see how it starts getting forgotten (even being powered with a big property like Marvel and The Avengers). Especially so if they had trouble building much momentum at launch, which feels like the case for this game. There certainly are examples of exceptions to this with games getting a revival or rennaisance years after initial release, but it's undoubtedly an uphill battle, and one that many games struggle to overcome.
Stuff like the Wakanda expansion sound promising at the very least, but IMO, it does feel like a lot of this stuff probably should have been pretty deep into development by the time the game launched, to minimize that gap in time between substantial content drops for this game. And that's unfair to some extent as we still have a Pandemic raging on, and all game development has had to deal with slowdowns related to that unfortunately. But ultimately that is the tough challenge of deciding to release a live service game at this time.