Those are horror stories, recall. If you want to write bad code then you can do it in any language. These stories don't resemble what I have experienced. (I work for a healthcare software company in Wisconsin.)
In particular, a sensible coding style and sensible development practices (yes, name your variables sensibly! yes, use source control! yes, have code review and automated tools to catch common errors) can remove the bad. It also helps if your company wrote its own (quite good) IDE for the language so you don't have to use Intersystems'.
Honestly the most fun thing about M/MUMPS/Caché is that there's very little boilerplate and you can write sensible code quickly. It's like being stuck with Java and then suddenly moving to Python or Ruby. (With, yes, a few pitfalls that these languages don't have, and quite a few features missing. I still prefer modern languages for personal projects. But you quickly pick up a sense for practices to avoid.)
I can't say all companies that use Mumps are great places to work. But mine honestly is. </soapbox>
In particular, a sensible coding style and sensible development practices (yes, name your variables sensibly! yes, use source control! yes, have code review and automated tools to catch common errors) can remove the bad. It also helps if your company wrote its own (quite good) IDE for the language so you don't have to use Intersystems'.
Honestly the most fun thing about M/MUMPS/Caché is that there's very little boilerplate and you can write sensible code quickly. It's like being stuck with Java and then suddenly moving to Python or Ruby. (With, yes, a few pitfalls that these languages don't have, and quite a few features missing. I still prefer modern languages for personal projects. But you quickly pick up a sense for practices to avoid.)
I can't say all companies that use Mumps are great places to work. But mine honestly is. </soapbox>