OK, I can understand that, you've seen what you've seen, I believe you 100%. I've found that when talking about any aspect of car maintenance with ten different people you'll get ten different sets of experiences and opinions, most of them not neccessarily wrong, just different. Same as I can only relate what I've seen and experienced.

I had a '95 Jeep Wrangler that I bought new, used Prestone coolant in it since day 1 (or since the first flush). When I sold it, it had ~125K on the clock, and the radiator and engine interior looked as clean as the day I bought it (I had to put a thermostat in right before selling it so I got to see the condition of the water jacket in the head). Granted that wasn't a sophisticated aluminum engine, but I used the same coolant in everything from vintage Mustangs to my Nissan 300ZX (which did have an advanced modern aluminum block and heads). The only thing I've gone OEM on coolant wise was my wife's '02 Jeep Grand Cherokee, because I couldn't find an aftermarket coolant that met Chryslers new spec at the time I did the first flush. Now Prestone, Peak, and a few others make coolants that are compatible with the newest Chrysler specs and I've been using them. It's got a very modern all aluminum V8 and so far no problems. Oh, and I change my coolants every year, not every two, I'm just a little bit anal that way, part of my spring car rituals.