What is this magical world you live in where a company can put up job listings for "Polyglot Software Engineers" and consistently, successfully get them through the hiring pipeline and staff up teams?
Where I live, (a) there's much more junior and mid-level talent with 0-2 years of experience than anyone else, (b) talent is far more likely to have TS/JS experience.
If you hire for JS talent, you ship. If you try to hire anybody else, you struggle to hire, struggle to collaborate ("I don't know X, so I'd prefer to open a ticket than to struggle and open a PR to that other team's repository"), and therefore ultimately struggle to ship.
Startups should run on the JS ecosystem by default and only write code in other ecosystems if there's a very good reason to do so (business competitive advantage, JS ecosystem options are severely lacking...).
Where I live, (a) there's much more junior and mid-level talent with 0-2 years of experience than anyone else, (b) talent is far more likely to have TS/JS experience.
If you hire for JS talent, you ship. If you try to hire anybody else, you struggle to hire, struggle to collaborate ("I don't know X, so I'd prefer to open a ticket than to struggle and open a PR to that other team's repository"), and therefore ultimately struggle to ship.
Startups should run on the JS ecosystem by default and only write code in other ecosystems if there's a very good reason to do so (business competitive advantage, JS ecosystem options are severely lacking...).