TL;DR: it doesn't suffice to fork the client, you have to fork the entire web.
Just because I disagree that things are worse that doesn’t mean that I like the status quo either. Which is why I use Firefox (well, one of the many reasons. But a pretty big reason).
I remember writing my own web browser around 1999 (give or take a couple years). Just a toy thing but born out of frustration with Internet Explorer, or Internet Exploiter as I used to call it. That was a massive undertaking. But these days if Google do stagnate Chrome then it’s still possible to fork Chromium and push it in a different direction. Not to mention we also have WebKit, kHTML and Gecko too. That alone makes this situation better than it was when Microsoft owned the web. Add to that, Chome doesn’t come pre-installed on as many computers as IE did (lots if you count Android but at least Apple hardware ship something else. Opinions of Safari aside).
This doesn’t mean we should be complacent nor assume Google doesn’t still have a stranglehold but it does mean the GPs point is inaccurate.