One issue though is that it seems more difficult to find competent developers for boring stacks, because they're always looking for the next challenge, the next thing they consider interesting or what looks good on their profile (vs what is best for their employer).
The people who job hop every 18 months and have flipped from ML to web3 to LLM's in the past 4 years are not the people you want to hire. If someone has 5-6 years experience writing Java code, they'll be fine if your tech stack is C#, and vice versa. There might be a bit of a learning curve pulling people from python or rails onto typed languages (or vice versa), but in my experience that's something that can be overcome easily enough. If you're willing to give someone a month to ramp up with the expectation they'll stay longer than 2 years, that seems to be a nice tradeoff to make.
So if I stay with a boring stack, I'd lose competitive advantage and face the potential of being "un-hirable" in the not-so-distant future.
vs
unix greybeard who writes bash scripts to grep secrets in git repo
They're the same, but the word salad ver is more understandable to VC and HR types
I mean obviously we all have to move ourselves from "Fortran boring" to "Java boring" every decade or two, but being un-hirable because of "Java boring" is not a thing.