This is actually a life circle.. we grew up.. we go to school .. we found a partner .. we start a family ..
yes normally the ladies will complain more than the guys because normally the wives follows the husbands. being a husband also isnt that easy because if the MIL and wife doesnt click, he will then have to handle two women very tactfully
now.. as we grow older.. we will too have kids.. and our kids starts his or her family. same situation if you son brings home a wife that you cant click.. then the table will be turned around.

yes. i have encountered this with my grandmother. she too was very toxic until the extend with a temper. so my dad and his siblings decided on moving her around families. that was how extensive the problem was and i remember the siblings having regular meeting to discuss before finalizing the plan to move my grandmother between houses. i cant remember how many month or months with each house. maybe this can be an option for you to try discuss.. but if the house belongs the your MIL.. then I think my option is not viable.