LLMs have a much larger training dataset of boring technology, thats also an advantage.

agreed. dealing with a complex polygot projeft. mumtiple mongodb, node hell, etc. hard to onboard.. or move fast

Another advantage of choosing boring/mature technology is that you have a broader base of talent to hire.

And that often means you can select across domain expertise, not just technical expertise.

If you are building a real estate SaaS for office managers and you build it in vanilla javascript and node. You have a base of 10k engineers available right now, one of which might have managed an office, or tried to be a remax rep. If you build it in svelte and the latest rust framework, you will probably hire 2 engineers specializing in that narrow stack