Firefox gets all their operating funding from Google’s Search agreement. This prevents FF from protecting user privacy as it’d jeopardize their primary source of income.

Firefox also has a lot of telemetry and experiments enabled, even if users opt out in the GUI. These have to be disabled in the about:config setting.

It is the slow and uses a lot of RAM, but despite all these thing it’s the second most popular for a reason (kept alive as an easy way for Google Chrome to avoid anti-trust)