All the legacy stuff you leave in makes the game more complex. It's extra cognitive load whenever dealing with the thing that has different versions. It's one extra permutation for testing. It makes the UI more messy for players, they need to make an extra choice etc. There is a huge list of reasons why you want to remove all legacy and all options.

Having options is nice, but claiming that it doesn't have a cost is being dishonest. Every single option is effort away from something else. So, for each option Larian will have to ask themselves, is it worth it or not. They aren't removing them because they are evil and want to take away your toys.