Earlier quoted context omitted.
My view is it's always organised elites making the decisions, no matter the system. Nominally left-wing parties often make brazen right-wing moves, and vice-versa. The votes that matter are those of the MPs, Congress members etc. which are always influenced by a range of factors and organised factions. That's the actual decision-making mechanism.
It’s the organized elites, true, but they aren’t a monolithic block either. In a proportional system they also must spread their influence on many parties. This is a good thing. With a single party there is a greater risk of a cordyceps infection taking over, see Republicans.
That and ensuring a bidirectional feedback mechanism between the executive and legislative branch, so that laws that aren't enforced by an administration fall off the books, and presidents that don't enforce the laws lose their job. Right now, the legal corpus of the U.S. is a constantly-accreting body, which means that no matter what the President wants to do, they can find some law somewhere to justify it, and then anything they don't want to do, they just say "We don't have the resources to enforce this". This gives the President all the power. They should be a servant to the law, not its arbiter.