I do agree to a point on your post...
The problem with the WDW monorails is that they are also nearing 30 years old and they look it. After enough time, no amount of cleaning, painting or repairs will make them better. Nobody is expecting perfection, but to expect functioning A/C, cabs that don't smell like a locker room and trains that don't have parts falling off them is a bit of a base level expectation.
The monorails are the first "ride" most people have at WDW. Right now, that first ride is little more than a city mass transit system, that looks like a city run mass transit system.
It sure seems like people are expecting perfection and cannot accept that A/C is a mechanical function, that might have broken just before you got on the monorail OR those trains, especially the hotel monorails, stop often with both doors open in the middle of summer in Florida, then load on a huge number of bodies all functioning at 98.6 degrees F only to do it all over again in just a couple of minutes. How fast or how powerful do we expect the AC to be to keep up with it. It's not all the time anyway, but, during high ridership times (opening/closing) I don't think god could keep it cool in those things. So many times the diagnosis if A/C broken is just nature against man situations. Nature usually wins.
Second point... in line with what was just mentioned... Florida, July, High Heat, thousands and thousands of sweaty, smelly people get on an off the monorail constantly, yet you expect it to smell like a rose. Also to repeat something I point out often. The smell that is being mistaken for urine or some other disgusting thing is the way those trains have been smelling since the first one ran. Whether it's the carpeting, or more likely the disinfecting chemical that is used daily to keep you whiners healthy is not really relevant, but, people are not generally peeing in the corner of the inside of a train car, in fact there are hardly any corners there to begin with.
Third point... can we get of the ridiculous notion that nothing ever goes wrong with mechanical things, not every thing is a lack of newness or lack of maintenance and not every thing can be predictable. One piece of a monorail, which appeared to catch on something, was torn off and fell to the ground and all of a sudden it's OMG the sky is falling. Get a grip folks. Those trains would never have run for thirty years without intensive maintenance, in fact it is likely that every part of them, with the exception of the passenger compartments have been replaced multiple times during that 30 year span. They are probably as new as one off the showroom floor in many areas.
Forth point... The monorails at WDW are nothing more then mass transit. They are multi-tasking as an attraction as a double benefit, but, never lose sight of the fact that are to take you from TTC, the MK hotels to MK and to and from Epcot. Just a fun way to do it.