The way I’ve always seen it is that there are different audiences/players for fighting games. You have the super casuals, who basically want to button mash and best up their friends and the AI. You have the extremely competitive players who play rather intensely online, go to tournaments, etc. You also have an inbetween group who learns the proper fundamentals and some advance mechanics, but don’t hardcore compete and usually mix Multiplayer and Single Player.
As such, I find different game modes are cater to different player types. Using Mortal Kombat 11 as an example, the super casuals aren’t going to dabble in Kombat League for long, and that game mode isn’t designed for them.
Likewise, a mode like Towers of Time, with typically poor AI opponents that are made tougher through modifiers, are not designed for the ultra competitive player, they’re designed for the super casuals so they have a challenge to face, solo, but also have means of overcoming the challenge (Konsumables and to a lesser extent, Augments) that they can earn/create simply by playing the game.
I’m okay with these different modes for different core player types, as I’ll simply focus on the ones that appeal to me the most. In a game like Mortal Kombat 11, there truly are game modes and types of play available for each and every kind of player!
In terms of locking items in that mode, they’re all kosmetic only and have no impact on actual kompetative play, many of the skins are simply pallet swaps and each character really only has about half a dozen unique skins, and more importantly, you can get them in other ways (i.e. Time Krystals, easily earned by playing the game as well as Kombat League).
In terms of playing things like Towers and if players will or not without the kosmetic incentive, again, that’ll depend on the player. For Mortal Kombat X, for the first few months, the Living Towers, which had modifiers but no real unlocks, was my main mode of play as I toyed with the game and learned the mechanics better. After that I started doing Single Fights as well as Private Sets with friends. Less of the latter since the netcode was still poor and frustrating at the time.