Just thinking out loud...
I wonder if the negativity around Onan propane generators is because there are no alternatives in the marketplace? I know I get frustrated when I am in a situation and have no options. Thus even a small technical problem increases my aggravation because I know I don't have any choice other than to accept it. If you want a propane RV generator, it is pretty much Onan or nothing. That allows Onan to charge a premium for their product. That in-turn creates an expectation of exceptional performance, and when something happens (no matter how trivial) it often creates resentment from customers.
Going to gas is not an option if someone wants a "propane generator". And, as noted on this thread, gas generators are not without their issues either. But unlike propane generators, there are plenty of options in the marketplace to keep quality, service, and price all in line.
Just a bit of rambling...
-Eric