It can be done. For it to work you need to remove VAR from the competitions (Competitions tab, look up every competition with VAR and start removing those things). I would advise to remove goalline checks as well then.
Next to that you need to remove it from the competition rules, which can be done via Advanced Rules. For national competitions that's not a problem. For international rules, both club and nation teams, it's a bit more work. I have done the removal on national rules previously (previous FM) and it's a bit of work, but it can be done. Never done it for international rules since I usually remade them for my own work.