If the application works, hire someone with design skills. They can work on contract basis as well.
Any suggestions for using Bootstrap or another CSS framework without using JavaScript? I'd like a pure CSS framework. Bootstrap looks good, but doesn't document what if any limitations will apply if not using their JS.
On top of that, it uses CSS classes for things like "this button is rounded" (https://bulma.io/documentation/elements/button/#styles) or "this tab bar has borders around its tab labels" (https://bulma.io/documentation/components/tabs/#styles).
The kind of CSS framework I expected was one that provides semantic classes for things like tab bars and similar, and then themes can decide things like "my tab bars should have borders around their tab labels". (And, as a side effect, the CSS would also be smaller, since it only needs a style for "tab bar", and not "tab bar without is-boxed" and "tab bar with is-boxed".)
https://getbootstrap.com/docs/4.5/getting-started/introducti...
I don't think anyone but you will be able to give an exact response to this. After all, it depends on your product and how you want it to look.
Remember, when it comes to design there are no universal right answers.
If you struggle with knowing where to even start, then working with a designer is probably your best bet.