Which part?

Firefox doesn't handle media playback as smoothly as chromium based browsers do. This is because of the codecs and plugins Firefox uses instead.

Firefox on Android is very clunky. Pull to refresh was in the beta for years, and they finally just released it into the main branch and it's bugged to shit. It was a meme how long it was in development and still doesn't work right, despite every other browser and app having pull to refresh work perfectly.

I want to be clear, I exclusively use Firefox and think chromium is dangerous for the web. I'm just not going to lie and act like firefox is perfect. If it was, it would have larger marketshare. There's a reason Chrome, despite being a privacy nightmare, is still at the top. There's a reason nearly every browser is chromium based.

I think being open about the shortcomings and experience you have with software is healthy. Good for development and good for making new users switch. Being critical is a good thing!