You're right the heat is a little bit of a barrier, but it's a trade-off. The areas that produce the most sun, also produce the most heat. The panels are tuned to do their best. There are cooling options, but I have yet to see many places implement them. If you have fresh water nearby, you can certainly liquid cool them, but then you start to cut into your power production.

Yes the dust is also an issue, there are automated ways to take care of it, and they're automatic ways to take care of it. It's also a trade-off. Sometimes the wind is sufficient to blow the sand on and off again.

It's all part of the calculations they do before approving a project like this.