I do think that the ST and any new Star Wars movies are technically unnecessary, but they have their place. The fact that the OT is a complete story means that the ST can’t (or shouldn’t be able to) take away from them just for existing and being at odds with it. You don’t have to acknowledge their existence or canon if you don’t want to.
So yeah, the new movies are a different universe. If you want it to be. They can also be the same one. If you want it to be.