"Choose boring technologies" is one of those phrases that makes sense when it makes sense, unless it doesn't. I find the negative expression of the same idea much more fitting: "Don't choose technology purely out of exitement".
In that negative version the word purely does the heavy lifting: If all you have as a reason to choose a thing is excitement it might be a bad choice unless you can afford a failed attempt.
In reality very often the "more exciting" choice will also come with their own additional pros/cons. It might be that your exciting Rust-Webservice has a smaller community backing its components, but maybe the APIs of the few components you really interact with is such a joy to use that it will save you weeks over the Java equivalent, while giving you magnitudes faster startup times and decent testability.
In programming there are so many angles to consider, that simplistic answers are rarely do reality justice. There is however the danger of wearing rose tinted glasses when weighing the cons of the more exciting solution.