Not so much because we're fed up with it as simply the performance characteristics of low end Android phones and the user expectations regarding mobile browsers not being compatible.

Startup time is just so darn important.

Not being able to rely on Gecko for stuff that must be accessible immediately means that Firefox for Android has to re-implement a load of things. That's not a choice that was made voluntarily.

On the contrary, if I'm not mistaken Firefox for Android threw out most of the "webbiness" in the UI and uses native UI heavily. That's why it's not portable to let's say Sailfish / Nemo and other mobile Linuxes, unlike the old XUL Fennec.

Not sure why it doesn't use IPC embedlite though when it's already went the native UI route. It's used successfully for the Sailfish browser (which uses Gecko embedding): https://wiki.mozilla.org/Embedding/IPCLiteAPI