Roughly two months ago. Windows and Android. A few things that make it very tough for me:

Autofilling. Chrome is just so much better and it's something I have to do a lot for my business. I'm always buying random parts from random places and a lot of them don't have the best-designed forms. Chrome handles them much better. There's just so much friction removed when you don't have to type all your info, especially on a phone, or pull out your credit card. I now have my credit card number memorized thanks to having to do so so much with Firefox. I had the same credit card for years, but with chrome I so rarely had to actually pull it out that I couldn't have told you more than the last 4 digits.

Chrome's built in password management is just better at picking up logins and passwords too when forms aren't designed really well.

I get a lot more performance issues with Firefox. I have to force close it sometimes. Never happened with chrome. It's not super frequent by any means but it happens.

Lot of websites don't work in Firefox and I have to open them in Chrome which is likely not Firefox's fault the majority of the time, just developers not testing in Firefox, but still quite annoying to me.

Not parent but in my case at least Twitch consumes twice as much memory to stream a video in Firefox as compared to Chrome, and still manages to stutter more. But it is possible it could be something to do with my extensions (uBlock Origin and HTTPS Everywhere) since they're installed on Firefox but not on Chrome.

Chiming in with a simple example:

Two finger pinch zooming on a Macbook stutters enormously in Firefox and is much smoother on Chrome.

I use this feature all the time and it's made switching to Firefox difficult.

Another example:

I'm not a fan at all of how Firefox handles displaying huge amounts of tabs. Tiny arrows to scroll your tabs left and right is really a disorienting nuisance and I much prefer Chrome's system of making tabs smaller. I'm sure there's a way to change this, but I'd rather stay on the default path that they're actively iterating on and improving.