These cars can suffer from a few issues related to the steering wheel position:
1. Bad steering wheel positioning from the factory
In some cases, the steering wheel in a Mirage isn't centered at the factory when the front end is aligned. So even if your front end alignment is perfect, your steering wheel won't be centered when driving straight down the road.
2. Bad factory front end alignment
In other cases, the front end isn't aligned properly from the factory and may require constant steering wheel correction to keep the car tracking straight ahead.
3. Defective rear axle
In the worst case, the torsion beam rear axle is defective and can cause the rear end to "push" in one direction...and require constant (and annoying) steering wheel correction.
My 2015 had both conditions 1 and 2 above from the day it rolled off the assembly line.
If your car tracks perfectly straight without corrective action from the steering wheel, then you probably have condition #1 above if your steering wheel isn't straight. But like I always say, every Mirage needs a 4 wheel alignment check...even if it's brand new.