Vivaldi seems to be doing ok and they only focus on a free browser. Brave seems to be doing well too, even if some of what they're doing is controversial. I admire them for at least taking a shot.
I don't necessarily fault Mozilla for trying to diversify revenue. The problem is when they neglect the browser to work on silly projects like Pocket, VPN's, mail relay, etc. and not even do a good job on those either. All of them were bolted on via acquisition or partnership, felt like an afterthought, and didn't provide anything that wasn't already easily accessible.
The organization doesn't execute well at any level and hasn't for a long time. They only exist because of Google and the remaining holdout users who feel obligated to use a sub-par, non-Chromium browser. I'm finally off that bandwagon. For the first time in over 20 years, I don't even have Mozilla's browser installed on my system.