Cars are commodities, and should not be sold by salesman on commission. I'm not buying another car until mine falls apart.
The term "commodity" typically refers to products that feature little to no differentiation between each other. It means you could largely "throw a dart" to pick one, and you'd be no better or worse off than someone who does meticulous research.
That you say you won't buy another car until yours falls apart already suggests that perhaps you don't actually consider cars to be a commodity. Sure, you won't upgrade in order to get a faster or more luxurious car. But I'd imaging from your statement that reliability is probably important for you. Although you don't state it, if you frequently have family with you in the car, or even if you don't, there's a good chance safety is important as well. Cars from various manufacturers vary greatly in both these respects.
Not to mention that for other people, sportiness, luxuriousness, ruggedness, storage space, and other factors are important as well, and cars vary on those dimensions as well.
If the vehicle market qualifies as a commodity, so are the majority of markets of any sort, to the degree that the concept of a commodity adopts a useless definition.
The sales staff are not competing against other dealerships of the same maker. They are competing against other makes. They are really selling you the brand.
Having said that, I think it's stupid that once you know the exact make and model you still need to deal with the sales staff. At that point, just give me the best price you have. You know what it is, you know what your competitors are doing. Why are we still talking?
Also, I don't know if you've noticed, but the landscape is changing. One of the big changes is that much more of the salesperson's income comes from salary and not commission. This is good. This means less sneaky tactics. Also, lots of dealerships now have an Internet department which will give you a quote online that is likely pretty close to your final offer. It's still worth trying to haggle, but lots of them don't have time for this: they simply give you an offer that's low enough to where you might actually just take it.
Simply put, replace build car > sell car, with sell car > build car.
As it is, car salesmen are nothing more than order takers that generate a large commission and overhead; the customers come to you. They only still exist because of massive regulatory controls that have created a dealership cartel.
Auto makers would become significantly more profitable in this model as well, no more massive piles of inventory or huge mistakes in guessing which models will sell. This ancient, backwards model currently costs GM and Ford billions each year in lost profit, and costs consumers billions in unnecessary middle-man mark-up.
The end result of this system is that inventory is borne by the dealerships, customers can personalize their cars (taken to the extreme with Mini) and the factory is a fascinating place to visit because every single car coming down the line is different to the one in front and the one behind. It is entirely integrated to their JIT systems soma truck full of steering wheels unloads them in the correct build order to match the vehicles progressing down the line already.
In an "Amazon Prime" world, few people want to wait 21 days for their new car is my hunch.
My father sold new cars ~30 years ago and custom orders were actually more common back then. Many dealers and volume manufacturers actively discourage custom orders now, even when customers would be willing to pay more to get exactly what they want. I think this is because of badly aligned incentives and will probably change.
If a customer walks in your door, you really need to sell them on your brand of car, at your dealership.
If the dealerships were manufacturer owned, perhaps the commission would be lower and service level higher.
Plus, you only go through the aggravation of buying and dealing with your DMV 1/3 as often this way...