Engineers like simplicity. It has fewer ways to fail. A simple solution that works for a wide range of conditions is worth its weight in gold.. literally, if you add up the development, maintenance, and repair costs.
Simple, widely-used solutions have a rich engineering history: whatever you want to do, someone has probably done it before. You can learn from their months or years of experience instead of having to do it all on your own.
That doesn't mean learning new hardware or exploring new solutions is bad -- engineering history has to come from somewhere after all -- it just means exploration is a choice.
If you want to learn new hardware for the sake of learning new hardware, the failures and dead ends will be more interesting to you than the things that work on the first try. Simple boards probably won't be as interesting as more complex ones unless you're new to microcontrollers in general.
When you want to do a specific job though, exploration tends to be more of a nuisance than a reward. For those projects, you want the simplest board you can find.