If it’s for a mobile game, the pixelation might not even be visible…
Avoiding this?
When you would make sure that you only have horizontal and vertical lines on your UV-map, you’d probably avoid pixelation.
(On the other hand you’d get stretching.)
If you have a square on your map and rotate that 45° that would become pixelated.
Generally, you set the resolution of your map(s) to fit the medium it is going to be watched on.
(Your tank would look horrible in cinemas, but on a small phone screen it might be o.k…)
I hope this all makes sense.