What objections exist to moving from majoritarian systems and reform transitions?

[James_S]

I've been researching different electoral systems after feeling increasingly disillusioned with the outcomes of our first-past-the-post elections, which often result in a majority government with a minority of the popular vote. I'm particularly interested in the practical implementation of mixed-member proportional representation, as it seems to balance local representation with broader proportionality. For those who have studied or advocated for electoral reform, what are the most common and substantive arguments against changing from a majoritarian system, and how have other countries successfully managed the transition to a more proportional model without causing political instability?