I don't think you are missing anything. It is far more attractive on mobile due the the extension support and hence ad-blockers. That alone makes up for any (small) performance difference Firefox has.
Chrome on mobile without uBlock is as bad as you would expect.
It's not 2008 anymore, there are choices beyond Chrome and Firefox.
Kiwi and Brave are both Chromium based, and on mobile both are faster/less jittery than Firefox. Especially on web apps that have some level of interactivity with CSS transitions and transforms.
Kiwi has excellent support for Chrome extensions including UBO, and Brave comes with adblocking built in. Samsung Browser has adblocking as well.
And those choices are literally rebranded Chrome - which means they're likely going to be victims of Chrome Extension Manifest V3 nerfing content blockers in various ways (especially once Chrome fully sunsets MV2), no?
No, V2 is being kept internally and exposed for Enterprise Chrome deployments. We at Brave have committed to keeping webRequest exposed to extensions too, while the underlying support remains and can be enabled for all Brave users.
Chrome on mobile without uBlock is as bad as you would expect.