How to find a main?

Hi folks :) Long time casual smash player looking to become more competitive. I enjoy playing a lot of characters (about 6?), but I know that lots of people only main like 1-3 characters and become SUPER good at those characters.

How do I decide which characters I should main and which ones should go to the curb? It’s so tough! Is there a methodology of which anyone knows?

My current list is: Isabelle, Incineroar, Robin, Lucario, Villager, and Rosalina & Luma.