I stayed 2 months on a 4 million LOC qt thing, it was quite awful. Like it was said, indeed, rewrite things slowly, or maybe rewrite the most essential parts.

Or just quit that job, it might not be worth staying there.

Resistance mean it is a situation of hostage taking: https://neilonsoftware.com/difficult-people-on-software-proj...

It's very serious and coders do this for job security. Don't accept this BS.