I’ve heard that because the F-35 has small wings it has to keep flying at a higher velocity to stay in the air. That makes it hard to support ground troops. It also burns up fuel so it can’t stay around long.
The A-10 can loiter for hours over an area and take its time... with a very big gun to shoot.
I’m sure the details of their flight envelopes are very different, but apparently the Brass want the F-35 to do all missions.