The guage isn’t all over the place. Some people had an issue with the sensor arm in the tank so it never reads full / empty but it’s still works in a fashion even with that issue.
The main issue is that when it gets low it suddenly says fill up with loads left.
Ultimately fuel injection and ECU fuel consumption calculations are very accurate. Your style of riding uses a certain amount of fuel and at least in the UK where we only have 95+ sold everywhere. I know to within 10 miles when I am running low just by miles done since fill up.
The issue is a small tank not the way it measures what’s left.