We write from experience. Most of my ~35 horses over the years were good at trailering. A few were not. DH retrained our KMH to load better, but we loaded him to take him home when we bought from the breeder, without issues.
What do you want? Solutions? Carte blanche to "beat up" the people who couldn't load your horse?
Horses need training. If you are happy with your horse's training and just wanted to vent...ok.
If you want good advice, read all above posts.
Do as you wish. MY horses load well. =D
And you as a shiny brand new horse owner knew all these things eh? Didn't sound that the OP was looking for solutions, just a chance to vent, which she did