This is, per definition, critical functionality, and we can't figure out whether it is working or not, and you are saying you don't care.
This is a pretty polar opinion right here - it's not a flaky test that fails once a week, it's unreliable critical functionality. If I were _your_ lead and you told me you fired someone because they spent two months on something, I'd probably fire you for not knowing what your team are doing for two months.
It may be unreliable critical functionality, or unreliable test. In some cases it's obvious which one it is, in some it isn't. If you know it's the test, it becomes much less beneficial to spend days on it.
And seriously, if you fire someone for having a strong opinion, you should remind yourself that even little kids tollerate a far worse behavior.
I hate the flaky tests just as much as a next dude but seriously, you need to factor in everything - deadlines, features, CI/CD, metrics etc, while still having constant time frame.
So lets not get into such polar opinions, its just not realistic at all. Life is never that ordered.