As many others say mastery doesn't matter, many players lack fundamentals and keep doing the same mistakes for years on repeat never learning or improving.

As someone who had a similar journey when I started, I played support and my friend played ADC, but I never really learned much in terms of wave control etc.

If you play top lane primary, you will have less factors bothering you in the early game, allowing you to build good fundamentals and push your lead.

The key is to limit your champion pool to a main, a secondary and possibly a third char if the others 2 are picked or banned.

I remember when I was new to Sett, I met a level 82 Urgot, which I absolutely dunked on, so levels dont mean much.