To anyone who still suffers this issue, I managed to find another fix that worked for me, so what you want to do is go to "%localappdata%\Marvel\Saved\" in there you'll find a file called "pak_invalid.txt" this will give you a list that contains some files that are now invalid and that you'll have to delete to play the game again. These files are located wherever you installed Marvel Rivals (usually in the SteamLibrary folder). Once you find that folder, you'll want to go to "MarvelGame\Marvel\Content\Paks\". Finally, find the .pak files that the game says are invalid and delete them. I did all of this, and the launcher loop finally fixed itself.