I like PR and similar systems a lot...
But you can't just dump a new voting system into our larger political system and expect it to work perfectly. Just saying right.. from now on, its PR, would be a disaster, and lead to all sorts of inefficient governance.
Generally speaking
FPTP is good at: Constituency level representation + Efficiently forming majorities.
FPTP is bad at: responding quickly to changes in public opinion + representing minority opinions
PR is good at: national level representation and quick responses to changes in public opinion
PR is bad at: creating simple and efficient governments able to enact change quickly, and make sometimes un-popular decisions.
I like the positive from PR a lot. For me brexit could have been either avoided entirely, or handled in a much much better way, if we had been living under PR for the past few decades. BUT to implement it you would need to re-structure our political and civil service institutions to counter the efficiency problems that PR creates. Our current system, unchanged, plus PR - would lead to constant stalemates and a complete inability to govern quickly and efficiently.