Is Firefox v chrome even relevant these days? I struggle to even think of shortcuts that aren't identical among the two browsers. Let alone UX and features.
I think the other big reason is availability of talent. FOSS is made by devs who usually are already well off and have time to contribute. You wont find as many artists nor graphic designers with the same privilege . so if there's bo designers on a project you get the bare basics.
You're meeting humans in interviews? That's already a big step up in this market.
The core negotiations are the same as always: know your worth , and only do it if you're willing to walk away from the job. But it's much harder to get that ability these days for many.
The only additional wisdom is to track layoff history these days. Getting an offer now may not mean you'll have that job in a year.