How to overhaul an entire application full of technical debt?

TLDR; How does a company go about overhauling the entire codebase to a new language/framework to keep up and remove technical debt.

I work as a entry level software engineer at a small startup. The code is very old and outdated with outdated languages. Now it’s very hard to find engineers who can work on the stack because there’s not many people at all that know the technology. My little junior dev dreams are to help modernize at least the front end with a new modern framework with something like React or Vue. The problem is that of course we don’t have many resources to even begin planning this out, it’s currently just out of the question given the amount of bugs we need to fix on a daily basis. How does a software company go about this given very limited capital? I feel like creating my own project and slowly start developing the front end components and when I have something substantial I can show the team. What are your thoughts?