a 13 or 13 Mini is the device will get hot quickly compared to Pro and Pro Max
The aluminum getting hot is a benefit, not a drawback. The heating means it's conducting heat away from the CPU, which is what really needs to be kept cool for long life of the device. If the steel isn't getting hot, it means the heat's staying on the CPU, which could fail faster because if it.
aluminum bends and melts very easily compared to steel
I'd be interested to know what you're running on your phone where it gets hot enough to melt aluminum!