I don't think it makes any difference what people call regional airlines. I think the label major airlines should be reserved for mainline airlines that sells their own tickets on their own routes. It's absurd calling CHQ or SkyWest a major airlines for neither one of them sells their own branded flying.
It doesn't matter what we pilots call regional airlines. What matters is how can we make mainline management take back all flying regardless of size, or route length and make all pilots under one company seniority list and pay same payrates and benefits.