Help! My Homebrew Sucks

I have been brewing extract-based beers for about a year-and-a-half now and I continue to be plagued by extremely weak-tasting beers. I thought I’d throw this out there and see if any other homebrewers have had similar problems.

I can’t track down what I might be doing wrong, but other homebrewing friends of mine are using the same extract kits and producing much richer, fuller beers. When you try most of my beers the initial flavor is fine but instantly drops off to water, with none of the malty richness you’d taste in even mild beers.

“Too little malt extract,” I thought, but additions of extract fermentables over and above that included with the kits don’t seem to make a difference. It doesn’t matter the variety, either; a Belgian wit I just uncorked tastes just as bland as any other.

Obviously there is something I’m not doing in the brewing process itself that is leading to the lack of flavor—there’s so little flavor in most of these beers that I’ve been just tossing them out, which is discouraging—but I’ve read dozens of books and howtos, bought quality equipment, and tried to take my time to do everything right. It doesn’t seem to have made the least bit of difference; the most recent beers I’ve made are nearly as weak and flavorless as the first batches I brewed almost two years ago.

This is the longest I’ve ever stuck to a hobby… and I’m not even any good at it. Any ideas?