While I agree that there are neck and hand shapes/sizes that make for a better match than others (basball bats for small hands or Wizard necks for someone who has finger like ET are prolly not the best fit), I found out through my own ordeal that the discomfort is more likely due to not taking care of our bodies/muscles and bad technique (forcing things instead of resting and playing with tense muscles and body)
I've gotten into this guitar workout spiral the past couple of years and last summer I managed to strain my picking hand so bad that I had trouble pushing down on a liquid soap dispenser as I "successfully" developed both tennis and golfer's elbow... Thankfully one of my online friends from another forum is a physiotherapist and he insisted that he can help me so we did 2 Zoom sessions (he lives in Italy) and boy was I amazed. He showed me a pre playing and after playing routine, both around 15 minutes and I am not touching a guitar without those anymore . All my pain was almost instantly gone and never returned. One of the most surprising things I learned is how the state of our ankles is connected with our shoulders.
In short (and without giving any medical advice) he explained to me that when strained, the muscles and connective tissues become tense to limit the range of motion to avoid further injury. Now until the tissues don't get back (or never had) proper range of motion, the pain won't go away and using the muscles in question will further aggravate the problem. So an easy set of warmup and stretching exercises solved my problem, thankfully.
Now I'm not saying that everbody has the same problem or thtat this is the sole source of their problem. This is just my sotry and food for thought. In a way guitar is like sport: you train your muscles to perform better. One doesn't play football without taking care of their body and muscles, but we, guitar players tend to forget that aspect of our passion. Some pain is OK - no pain, no gain. But we have to learn when to stop and how to take care of our body. Some guys are lucky and never have such problems. I am not one of them and I am thankful that I had a chance to learn how to avoid bigger problems.
Count yourself lucky. I have tennis elbow in right arm, which is now just subsiding after about 15 months. Course of recovery can be up to two years and I put myself in that category as I can still feel issues. It may never go away.
Ive watched tons of videos, performed "at home" PT, got referral from doc for real PT but because of Covid was not able/unwilling to mess with exposure/time/expense.
From my reading, PT for tennis elbow is not much better than placebo. Some people are long haulers and need significant time. Ironically, the exersize which helps me most is reverse finger extension (put fist in sock and open hand) which is not common PT for TE.
It was not caused by playing, but by guitar maintenance, a period of two weeks where I decided to level, crown and polish all my guitar necks. I probably put in 40+ hours of back/forth filing and polishing moitions in a very short period of time. I haven't played guitar since then because unsure if picking motion will exacerbate problem. Also afraid it will get worse as spring is upon us, yard work, washing cars, etc, had made it worse last summer. Its been a serious problem for me.
My left arm also screwed up by a completely torn bicep about five years ago. Had to go through surgery, change my playing position, etc, which probably altered my RH picking enough to cause the TE. It certainly limited range of motion just enough that to vibrato I need to sit in classical.
Both of my arms are fucked. I haven't picked up guitar in 15 months. I am patient and believe I will play again.
I just wanted to point out that your recovery from TE, from everything I read about course of recovery and the role of PT, is probably just luck. PT has very low success rate for healing TE.
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. Tiny frets, which made it "as fat as could be", - modern frets would have made that neck way huge. hehe. 
