Google has been dodgy for a long time. They've been abusing their dominance to maintain their monopolies and erode our freedoms. No matter how many times developers like that of uBlock tell you that the blocking experience isn't as good in Chromium based browsers compared to Firefox, due to decisions made by Google, people don't listen. Now Google is attempting to insert DRM into webpages to force us to look at their adverts, that's insanity and everyone knows it. But still people support them by using their products. I can understand using YouTube, no other video site comes close in terms of content. Gmail is the class leader for email. But search? You can't even get results on the first page without an adblocker. And their browser, along with the derivatives? Why are people empowering Google's fuckeries? It makes no logical sense. People even attempt to hold Firefox to standards they turn a blind eye to for Chrome. I'm baffled, confused, perplexed by it all. I just don't get it.
There is a shockingly large number of people who go through life in general reacting to things around them and not thinking critically in any meaningful way. Chrome is "normal" to them, it's the default, the status quo. On top of this, our monkey brains tend to rebel when asked to consider making even the slightest change. I'm a bit guilty of this as well. For example, I stayed on reddit for years, even though it wasn't something that was an essential part of my life and was clearly harmful.
The reason people are more critical of Firefox is that it is different, an outlier to them. Maybe they think it's too confusing to switch, or they try but they never get past that initial feeling of discomfort from even the slightest of changes, never give themselves a chance to acclimate, never learn how to make it a far superior browsing experience to Chrome.
Then because it is new and different, such people will start to perceive everything as dangerous and bad. That's why people are still saying Firefox Mobile is slow and buggy as an excuse to stay on Chrome, in spite of the fact that all metrics say otherwise.
(Note: This doesn't include iOS and Mac users, for whom Firefox is basically a worse Safari, but that's thanks to Apple, not Mozilla.)