So you've sought professional training for everything you do in life? Do you feel national level shooters that tweak their triggers/gun/equipment have no understanding of the fundamentals? Your taking your own life experience and your own ability to learn and applying it to everyone else. People learn differently. While I completely agree professional instruction in ANYTHING will likely be beneficial, their is a lot to said about doing things on your own. I say likely be beneficial as a bad instruction can do more damage then good.
I recently built a cottage. If I understand you correctly I should first have gotten carpenter training, then I should have gotten electrical wiring training, plumbing?, Hvac? I read books, bought the electrical code simplified (a book), checked the building code, used common sense and consulted the almighty internet when I wasn't sure. So ya, I "taught myself something I don't know" and gained skills and knowledge I will have for life. I made mistakes and learned from them, I took longer then paying a professional contractor, I had to buy tools I did not have. The personal satisfaction and money I saved far outweighed any of the negatives though. I often find the people most adamant about not trying to do something on your own are those that stand to profit from it. Are you an instructor by any chance? I didn't enrol in trades training and get a carpenter/electrician/plumber/whatever else ticket but was still successful.
Ill take the same approach now, read a lot, trial and error...see what works for me and what doesn't. I won't pay someone to show me how but I'll still be successful. Remember success is a moving target defined by what a persons goals are. I'm not a national level competitive shooter in training nor do I want to be.
I enjoy my range time, never walk away frustrated (a bad day at the range is better then a good day at work). I walk away with learning something new and satisfaction as my groups shrink.
OP sorry for getting off topic...
Try the Ghost EVO connector if you want a really sweet trigger. Instantly shrunk my groups!! (did not improve my form, trigger control or other fundamentals however). The best part was I did not need to take a glock armourers course to install it, I just watched a utube video ;-)
TDC - I respect your opinion, you seem knowledgeable and perhaps I'm just ignoring good advice but I think I'll be fine right now based on what my goals are.