Do E2E testing, test the API. If you later find out that the implementation is lacking, yoi can swap it out with confidence, if you have 100% coverage of your API spec.
Also, as a sort of management recommendation, you need to set the bounds and find the people that can work with you, not the other way around. (Yes, of course, you work with what you have, but this doesn't mean anything implemented in spare time must become the next cornerstone of the company/product.)
And you must spend a lot of time growing your teammates. Because with a great team a rewrite/refactor will lead to better results, with the same quality team, even in a "better" language you will only get similar low quality results.