Marvel's Avengers Game Shut Down After Struggling to Meet Lofty Expectations

Marvel's Avengers was conceived during peak Marvel mania, so it focused on the exact Avengers from the MCU rather than new takes. This led to immediate buzz issues.
The campaign is quite good, but the forced live service looter gameplay feels unrewarding since there's no real loot or cosmetics.
The amount of content needed for a live service game proved too ambitious, with constant delays and content gaps.
Crystal Dynamics tried hard but was given an almost impossible mission between Marvel expectations and content demands.
The game is now being completely delisted and will receive no more updates, a somewhat sad end for a game with some strong points.

forbes.com

Relevant topic timeline:

9/17/2023

Marvel's Avengers 90% Off on Steam Before Delisting on September 30

Marvel's Avengers is being removed from digital storefronts, but developer Crystal Dynamics has lowered the price to almost free in order for players to secure the game before it is delisted, with support and events continuing until the game's official support ends on September 30, 2023.

10/1/2023

Marvel's Avengers Officially Delisted as Live Service Experiment Falters Despite Popular IP

Marvel's Avengers, a live service game featuring Earth's Mightiest Heroes, has been delisted from all digital storefronts, signaling its demise due to its failure to attract a sustainable audience despite its potential as a solid single-player and multiplayer game with a diverse cast of characters.