That’s called Aliasing and there are several ways to make it look better which is called Anti-Aliasing or AA
from what i have experienced so far your phone’s screen resolution will affect your AA and you also need to use better AA methods like mobile msaa but that comes with a cost.
try these commands below on your package: (hold 4 fingers on your screen and a console will appear and also make sure its a development package not shipping or else console command will not appear.)
- r.mobilecontentscalefactor 0
- r.postprocessaaquality 3
- r.mobilemsaa 4