It's not a new feature, not especially attractive to average joe and I don't really think average joe even cares about features as long as Youtube, GMail and Google Drive load.
They already were the first? I still remember when I upgraded Firefox on my phone and all of the extensions were gone. It's nice that they're finally bringing them back after all these years, but it's just a return to the way things used to be.
EDIT: Headline here was changed from the original article, which doesn't claim "first", just "only".
Unless things have changed, Apple's policy of generally not allowing programs to download executable code would block this. Browsers are locked into using Apple's allowed web engines because of this, so basically every browser on iOS is safari or re-themed safari
It looks like support is either up to the developer or simply optimization is up to the developer. They mention that extension devs should start optimizing their desktop extensions for mobile but doesn't say whether that's required or simply suggested as a non-optimized extension may not work properly.
But theoretically, any extension at the very least could be made to work on mobile. It appears to be an open system as opposed to now where it's only approved ones.
Also Firefox mobile already supports (a tiny limited subset of) extensions. And the version before their big UI overhaul supported extensions from the add-on store - although it would be unusable if you loaded up too many.
The big change is that the new shinier faster version of Firefox will now support their new desktop extension platform - and probably run them much more efficiently.
Pretty sure the person who wrote this headline only ever used Chrome mobile.