Everyone is capable of learning. I can hire someone who is capable of learning Japanese. They can then try to teach the rest of the team Japanese. Does that mean it's a good idea to switch all our internal docs to Japanese? Maybe if I was building a startup in Japan. Similarly, writing internal docs in English for a startup in Japan would be of equal difficulty and value. Hooray, we're learning! And struggling more than needed to build a product.

You're better off hiring experienced people who are highly productive. If they're highly productive with one stack, it makes no sense to change their stack so they're no longer productive, or hiring people who aren't familiar with it and waiting for them to become productive.

There's nothing wrong with using old, well established things. They're quite often better than new things. As long as they're still supported, just use whatever builds a working product. It's the end product that matters.