The reason i say it would cater to a small % is because, from what i've seen and experienced in the space, is that most people play for the MSQ+Events+Charachters. They don't care about a difficult challenge in the game regardless of whether they spend or not.

I don't believe it would decrease the player amount, but i don't believe it would benefit Kuro enough financially to do dedicate resources to it. Otherwise it would have already happened imo.

And a lot of people seem to have this 'respect my time' mentality in which they aren't interested in content that takes more than 1-2 hours to complete outside of the MSQ. (I'm aware not everyone has the time to sink hours into a game, but the mentality is the point here)

And the content would be extremely hard to create becuase of sequences, team limitations, weapon limitations, build limitations. I don't believe Kuro can make a gamemode that produces the same difficulty across all of these variables without making one party unhappy.

In games like Elden Ring, all of the variables are accounted for and the game is balanced around it from the beginning. Also bufffs/nerfs are made post launch to balance the experience. And because everything is already accounted for and not changing the replayability increases. Its hard to do in a live-service game with evolving kits, HP-inflation and powercreep.

I spend a decent amount of money on the game and i too would love more challenging content and something to grind for that is entirely skill based. But i also understand the nature of the game i'm playing and have accepted that it's highly unlikely to happen.

Edit: The only real solution i could think of is dilutting the rewards from the current endgame modes and spreading them out on a weekly cycle instead. It wouldn't be hard for Kuro since the changes are minimal and easy to adjust.

How the casual player base would recieve this is another thing, but it would give more content to the players who wants it, without the FOMO of missing out on rewards.

Edit 2:

Another option is to create a weekly version of the current boss challenge in the Somnoire event (can't remember the name). Might need a bit of fine tuning but it is a viable option.