I actually wonder about that. So Firefox is seemingly becoming more corpo in their approach. Their home tab now has random adverts and suggested sites that I should visit. I guess the general vibe that I'm getting is "sleek, polished", which triggers some latent suspicion about the way they are headed. As many people, I keep returning to Firefox every year or so, just to see whether it can be transitioned to. Maybe that's why it's so jarring.
I am also worried that "Firefox is the only real alternative" is not a healthy state of things. We get Chromium flavors, high maintenance nonsense, and Firefox.