Why so? Its worked very well for generations - and it makes getting rid of corrupt/useless/incompetent PM’s a much easier (and quicker) process, limiting the damage to the political system.
What i have in mind is a system similar to the American one.
Each party provides a list of candidates for the job.
These then have a Presidential (Caucus) style campaign for election.
Then at the Ballot for the local MP there is also the candidate for PM as supplied by the party of your choice.
(Pick the local tory, then tick one of four for PM)
Then it is a simple matter of choosing the combination of, “Ball less”, “incompetent”, “Out of touch” ,”Slimy”, etc, that floats your Boat.
All of the usual ‘tool’ removal tools would remain in place.
It is just a thought ,could make for some interesting debates.