These include constant removal of features, bad coding paradigms, poor memory management, and hidden telemetry. In short, Firefox simply doesn't work that well anymore for developers or ordinary users who just want to use their browser, thank you very much.

People look for software that's easier and feels good, and Firefox simply isn't smooth, doesn't offer as many features out of the box (even some common features), and it doesn't work as well. You might be a power user, but most people don't want to have to jump through the extra hoops.

Extensions and themes can cause Firefox to use more system resources than it normally would. To determine if an extension or theme is causing Firefox to use too many resources, start Firefox in Troubleshoot Mode and observe its memory and CPU usage.

Firefox loads extensions when it starts up and many extensions add startup tasks. If there are too many extensions installed, this may cause Firefox to use more system resources and then slow down Firefox's speed. You can switch to a different theme.