It's rather discouraging to read all this - I've loved puppets my whole life and have always wanted to do something about it. But I give up easily and I don't know if I even have the skill - it would be heartbreaking if I didn't :/
I know exactly what you mean, I've been doing puppetry for a year now, and throughout the past year, I've learned so much, and I'm proud to say that I've improved alot, particurally with building puppets. I still need to improve a little with moving the mouth of a puppet and writing for puppetry, but I'm sure after another year or two, I could confidently say that I am a puppeteer, but doesn't mean I'll be an expert or anything, because I'll still be learning. I believe that in anything you do, you always learn as you go, because no one knows everything there is to know about anything. You could be an expert in something and still be learning.
For example, I know a puppeteer, who's been doing puppetry for over 30 years and he told me, he's still learning and will continue to learn, because he doesn't know everything there is to know.
Another good example, I once e-mailed Rick Lazzarini, who provided the animatronic puppets, and special effects for many films, including Alien and Spaceballs. So, after many years of experience, he told me he was still learning.
So, just keep at it and you'll get somewhere. I'm sure even Jim Henson, Bil Baird, Burr Thomson, or any other famous puppeteer, felt the same way you did, but it took them a couple of years. Just keep at it and hang in there.
Hope this helps!