I think that folks who want "level 0" in 5e are missing the point of earlier levels in 5e.
In 5e, if you have a group of experienced players, you start at level 3. Because that's the level at which classes have their full toolkit and feel reasonably complete.
1st and 2nd level are tutorial levels. You use these to represent characters who are underexperienced, or younger, or whatever; or if your players are new to the game, so that they aren't overwhelmed with mechanics.