I don't like the idea of a beginning at level 10.
Level 10 characters are totally different in comparison with lvl 1. They are OP, have many features, powerfull spells, abilities and proficiencies.
They also had chosen their subclasses...

We have to start at level 1 to feel this character is pur character, to learn how the game/classes works and to feel out progression from no one to hero.

On the other hand, I hate what you describe and have the same feeling about the consistency of the experience.

I agree with your statement but not with the solution.
Anyway nothing about this will change so talking about this is not constructive (I don't mean that you shouldn't of course... But I personnaly won't write lines and lines about something that is totally definitive)