Googlebot is getting non-javascript version of the site

It’s really easy to make claims like the above, particularly when by your own admission you don’t understand the inner workings nor design decisions which led to the current state.

Realistically speaking though you can’t guarantee anything here, and unless you can convince someone with the requisite skills to alter the code it’s going to remain hypothetical.

If you have a budget to explore this the Marketplace might be a good starting point.