If you really want to help Firefox succeed, file a bug on https://webcompat.com/ when you find a broken website. Don't just switch back to Chrome; let Mozilla know there's a problem so they can try to fix it.
When browsers lose market share, they fall into the "compatibility death spiral." Sites don't bother to test, they break, and users flee to the browser that "just works." Mozilla is fighting this battle every day, and it just got harder.