Uneven wear is often caused by aggressive driving (e.g., constant drifting or hard braking) or mismatched tire hardness for the surface.
For example, soft tires grip better on dirt but wear fast on pavement. Replace tires with ones suited to your terrain (soft for dirt, hard for asphalt).
I bought drift tires for my MJX Hyper Go 7303 RC car from this store, so you can go in and check it out too:
MJX Hyper Go 1/7 7303 Rally RC Car Parts White Wheels