>> Build systems are inherently unreliable and periodically require full clean
What frustrates me above all else is the trend of compile-to-javascript languages. IMO interpreted languages are great, of course some performance was sacrificed to get there - I think that was a fair trade-off because saving the developer from having to build the project is a HUGE advantage when developing (at least for my particular development flow)... So when I see people throwing away that massive advantage by adding an unnecessary compile step in order to get slightly better syntax or static typing (e.g. CoffeeScript or TypeScript), I find it deeply disturbing. Static typing can be a useful feature, but is it worth adding a compile step? Not by a long shot.
And the idea of transpiling a language into an interpreted language is just ridiculous in principle. We had an army of very smart people who invested a huge amount of time and effort into making efficient interpreters for certain languages but all that work is thrown away as soon as you add a build step.
And the stunning thing is that it's actually possible (easy even) to create excellent software with clean code without a build step (I've done it many times) but these simple, clean approaches are never popular. People want to use the complex approach that introduces a ton of new problems, delays and compatibility issues.