You're not wrong, but the last time I checked modders have only been making skins for characters to make the game look goofy as hell. I'm not saying people won't do it, but it won't be publicly available meaning very few people will have it unless that modder is looking for trouble with the game studio. At that point I wouldn't argue with them to ban modding. Don't abuse the power you have. It's very simple to understand.
I don't fully disagree with the point that Marvel Rivals needs support since its a free to play game, but banning mods isn't the way to go. Modding by itself creates a whole community and makes them want to play the game to see what new models they can create. The player base will support the game if the creators of the game are doing a good job and listening to the community. I haven't downloaded mods myself, but I've already put money into the game because it's a fun game and the characters look great. I'll support something that I like and marvel rivals hasn't done the community wrong yet.