You are correct that if one models a concept with a small scope, S scale can fill the bill.
Yes, there was a lot of product made over the decades.
If one can accept the limitations imposed by the state of S scale: One's S scale boat can sail merrily off into the sunset.
The caveats for me were:
* Though a lot of product was made over the decades, the trick was trying to find it, obtaining it, and if you do obtain it, then often you had to get it up to one's personal goals in looks and performance. Those aren't easy tasks for many modelers. The only products that performed in a manner I was used to (HO Kato-type performance) were the engine products of SHS. All the others had to be fiddled with and often re-powered, or worse.
* Plus, no matter how you slice it, the variety just isn't there for diesel-freaks like myself that like a wide spectrum of engine makes, models, variations, etc. The main downfall point for me was switcher selection. (At the time I was going to attempt an urban KC industrial switching district.) Aside from white metal kits for an EMD and an Alco S, or a limited run resin flat-kit for an FM, your only two options in easily worked plastic were SHS EMD's and AM's Baldwin S-12. Unfortunately, the AM S-12 has road trucks under it which really needs to be replaced with the correct type trucks for the engine to ever truly look like it should. Guess what trucks it needs? Yup, SHS trucks that SHS used under their EMD switchers. Those are long gone as single purchases, so now the only way would be purchase an SHS EMD and take the trucks off it. When finished adapting the trucks to the AM frame, you finally have a Baldwin S-12 that has accurate trucks... and a high $$ SHS EMD that doesn't.
Then there's the ubiquitous GP7 in S scale: None. You have to purchase the AM GP9, then find/purchase the GP7 long hood kit and bash/modify to get a GP7. The railroads I was trying to model had scads of GP7's... but only a few GP9's.
I truly gave it the old "Gung-ho!" attempt to model in S:
Now, IF I had been able to accept the following:
* Go with high rail wheels.
* Go with a track system available for same.
* Accept what could be found and obtained, and accept that additions to the S scale offerings were going to be a long time coming, or never.
...then maybe it could have turned out different.
However, I couldn't accept the above then, and doubt that I could now. I still seem to enjoy small profile rail and product variety way too much. (Besides, IF I was going to up-size, it would be because of dexterity and eyesight issues, and then it would be traditional 3-rail, with a heavy Lionel PW presence, and enjoy model trains until I can't.)
Thus I wasn't able to "do it my way" in S, so I made like a rat and abandoned ship.
Andre "Fleeing Rat" Ming