I appreciate your whole post and agree with it in large part. However, this part sticks out to me. I understand why this is the advice everyone gives. Heck, it's probably the advice I would/do give. However, I think it's flawed in some way also. Before going down my 4 month Beretta rabbit hole, I spent $300 + travel and ammo with Larry Vickers on "Advanced Pistol Marksmanship" and $425 + ammo (class was local) with Gabe White on "Pistol Shooting Solutions."
I think most would agree that these are "good instructors" and I learned things from these classes, but neither of them taught me what I learned about trigger control from 4 months shooting a Beretta.
At the risk of sounding arrogant, maybe some of this has to do with "levels" too. A beginner shooter might have learned a lot about trigger control in those classes. However, there are degrees and levels to this stuff. The trigger control required to shoot a 3" group vs a 6" group at 25yds are a bit different (just as an example).