Idk about 12 years but I know about last two years - many companies and workers had to switch to WFH. So that means using some sort of chat&video&audio software/website. What did Firefox do to fix the compatibility e.g. with Teams? That should've been the highest priority. Instead, it took them years to get at least the GPOs right, autoupdate is the same story... so many things in corprote env were or still are PITA…
1. Google basically controls the web.
2. Whenever a new Web API shows up, browser vendors have to decide between implementing the standard and copying the bugs, exotic behaviors and extensions that are implemented in Chromium.
3. Websites are tested on Chromium, so they start to rely on Chromium's bugs, exotic behaviors and extensions.
4. When a website breaks in Firefox (or Safari), people claim that it's the fault of Firefox devs and switch to Chromium.
The early web got tired of this when it was Microsoft at the wheels, but it feels that few people are particularly interested in fighting the good fight these days. Much easier to blame Mozilla.