It's fine to be skeptical of how casting was handled. But it seems odd that they would try to find a proper actress for Mirage (Blu Hunt?) & Cece Reyes (Rosario Dawson?), and suddenly not want to do the same for Sunspot.
Where's your proof that they didn't try, ran out of time, and had to settle?
I get that it's not unnatural for Hollywood to get these things wrong. It happens all the time. But you don't see me going around saying "**** Boone and anyone who would defend him." when casting isn't always in the directors hands.
You have the right to be mad at the casting, and I have the right to give him the benefit of the doubt, because of the two potential actresses listed above.