Chrome may soon give Firefox a little win here by nerfing uBlock Origin, but is that enough?
For most of (former/present) Firefox users extensibility wasn't the "killer app".
FF gained its marketshare at the time because IE was so crappy on most metrics and that was the main competition.
But as the article explains, this was largely caused by the need to provide extensive backwards compatibility which stifled innovation or completely prevented it (in case of multi-process architecture).
But whoever kept Firefox after Chrome gained popularity probably do so because of the extensions.
It's a matter of getting the word out. Mozilla likely won't outright bundle its features as to not completely alienate Google, since they are their main source of revenue, but seem to be okay with promoting it otherwise, as it is on the front page of addons.mozilla.org and was the first extension (and the only one, for a time, and still only one of nine) supported in the new Firefox for Android.
There are also "normal" users who do not care about blocking ads and tracking, or do not know about the performance issues, malware risk, and other reasons for using a blocker and have not made such a decision, trusting the browser to act in the best interest of the user. (We know that last bit doesn't work anymore.)
(Regarding uBlock Origin, gorhill has expressed that he will not neuter the extension to work with Chrome's API change, reference: https://github.com/uBlockOrigin/uBlock-issues/issues/338#iss... )
Also, the comment you describe is from May 2019, so their timeline of "within the next year" is already refuted by reality.