I'm not sure why people are misunderstanding my question as "Why not bring more fuel and burn the rockets in reverse". I am simply asking: why not reenter the atmosphere at a shallower angle, spreading the atmospheric braking friction over a longer period of time, which I'd expect would allow more time for the accumulated heat to radiate away before it becomes catastrophic.
What makes you think they aren't already taking the shallowest possible descent?
Once you start touching the atmosphere, it very quickly becomes deterministic. There are a limited number of descent profiles that actually get you to the ground, and believe it or not, starship as far as I can tell is actually taking a "shallow angle" and spreading the atmospheric braking friction over the largest possible time. A steeper entry would melt every conceivable material
I'm no expert but I think reentering at a shallower angle results in "bouncing off" the atmosphere. So, even if you did it multiple times like a rock skipping on water, you'd have to have extra fuel to counter the bounce "up" and go back down for each skip. Thus, back to the same "bring more fuel/weight to orbit" problem.
Any heat you see is velocity lost to the craft will eventually hit the atmosphere again. I think the main reason is that the skip and the second reentry is way less predictable than doing the descent in a single pass so for predictability of landing agencies much prefer to do a harder more controlled reentry.
