I've spoken with Garmin customer service several times and have had no problems with them other than the one time there was an hour wait on the phone to get through. I was with Panther at the time so I didn't even notice that it was a long wait.
You're right about one thing, though, they have no interest in making a unit that can be reprogrammed by the end-user. It would be cost prohibitive, and they couldn't possibly hope to offer any kind of tech support for such a unit. But, if you're willing to pay the costs of development and production, they'll make you any kind of unit you want. For several years I was a beta tester for Garmin and ALK, so I know what all goes into the programming, and why it's simply not feasible to just open it up for countless user-modifications. Some of the very things you are complaining about are what the customers wanted most. Auto recalculate used to be an option that could be turned off. But most people wanted it, and they had a ridiculous amount of tech support calls from people with it turned off who were complaining that it didn't work. So they turned in on and removed the option to turn it off. To say they don't listen to customers is just incorrect.
You want one until to do what you think it should do, and do it the way you want it to do it, but if you think about that, it's a little silly. It's not designed to be all things to all people. But it does seem to work quite well for a rather large majority of people. How many things do you own that will do everything you want them to do, and can be easily altered by anyone else to do exactly what all they want it do to, too? I assume you only have one gun, then, correct? Because one gun should be able to do anything and everything a gun should do. No need for a duck gun and a rifle and a handgun, right? When you go duck hunting, why do you use a boat and not your truck? Seems like a good truck should also be able to float, or at least be easily modified for duck hunting.
I have a Garmin, DeLorme, Streets & Trips, and PC Miler, and there are major differences between all of them. But they all work quite well as long as you understand they are tools with limitations to be used within the parameters of what they are designed to do. Instead of griping and moaning about what they won't do, it's better to learn what they will do, and then use those tools as needed. Become the master of the tools, instead of getting owned by them.
They funny thing is, there are very few things DeLorme (and the others) can do that the Garmin can't. But the Garmin won't do them in exactly the same way DeLorme will. Same with Streets & Trips, very few things it can't do that the Garmin can. The Garmin can import databases of locations, pre-plan trips with precise routing, export and import maps and routes, the whole bit. But, you've gotta invest the time to learn how to tool works, to make it do what you want, just like you did with DeLorme.