Dent repair is not as black and white as you're making it out to be.
You need to study the cross section of the dent and realize which way it has indented. Sometimes it cheats to one side or the other. Pulling it straight out or the wrong way can make it crinkle on itself.
It takes experience to know which way it naturally wants to relax and to help coax it in that direction.
You might get lucky wth your method or you might make it worse. I personally don't trust myself enough to attempt it.
I agree with you 100%
Tried a few of the do it yourself dent repair kits where you use the hot glue gun sticks like the OP mentioned. No matter what prep I did I never had the post stick long enough to pull out a dent. (My nephew and I were practicing on a parts truck)
There was a dent near a side mirror and pushing out the dent from behind, accessed with the window down and enough room to push on the door skin, and I thought it would look better pushed out and I was wrong. It had new creases and looked worse!
My experience was more mechanical then body work and it is not as simple as it looks unless you have the training and experience.
What opened my eyes was when I saw a demonstration where dents were removed with heat, special tools, and how a hood with a bunch of hail damage was made good as new without any body work. I was amazed because I had no idea how far the process had come. I was old school where the hood would have been sanded, dimples filled with filler, sanded, painted. I have a few door dings on my Monte and would have this kind of service done knowing that all the dings would be gone in a few hours instead of weeks the old way.