How do you all manage your MILs?

My partner (37M) and I (41F) are not married yet but I am contemplating ending it because of his family, especially his mother. For those of you who went ahead with marriage when the MIL was clearly difficult, how do you manage it knowing what you were getting into?

I have limited the time I spend with her and don’t react to her games (they are so obvious, she seems very foolish) but my partner is the issue where he doesn’t always put up boundaries with her. Sometimes he does, sometimes he doesn’t. There in lies the problem.

I don’t have these dramas/issues in my own family so to chose to marry someone where I will inherit all of this seems like I am sabotaging myself and setting up my relationship for failure. By this stage in life I have no time or tolerance for her behaviour.