I'm not so sure about that. Complex solutions are mostly prebuilt, and used by thousands. When any one person solves an issue, that's usually the end of it, so it gets more reliable over time. Even Windows seems to have gotten better.

Simple solutions still have a nontrivial amount of code(Otherwise the whole project would just be "use this turnkey app"), but the code is original. It's probably still going to need debugging.

Complex solutions are mostly prebuilt, are used by thousands, and still are horribly buggy. Your typical app or website - say, GMail - is much more buggy, from the user point of view, than its counterpart, say, twenty years ago. We've just learned to be blind to most of those bugs.