Sheldon is more than just a supporting character

https://screenrant.com/young-sheldon-season-6-show-better-without-character/

You're wrong, Screenrant. If Sheldon goes, the show ends.

As to his storylines not mattering, that's nothing intrinsic. It's just because of the way they're writing it. They could write it the other way so that his storylines are the only ones that matter. So you're wrong there also.