Obviously they won’t because that same system put them in power

Yes

and is currently holding far-right at bay

No, they’re acting as an establishment backed placeholder while the right regroups in preparation for a surge even further right next elections (when they get to blame all of the countries problems on “lefties”). Also the far right has made pretty significant gains this election.

Either way though you’re right - he has no reason to fix the voting system. People really need to let this sink in - Starmer isn’t there for the good of the country or the people, but his own and that of the establishment.