In practice the electorate has to make a pragmatic selection between the choices available to them. Once party leadership and policies emerge, those are your choices, neither may be ideal but that's what you've got. You might very well suspect the politician you vote for won't achieve everything they want to, but maybe they'll deliver more than the other politicians. That sounds terrible, and it's not great, but at least it's realistic.
In direct democracy there's the illusion of zero compromise, you can end up with whatever wacky or amazing combination of initiatives you like, but in reality compromises still have to be made and priorities are going to conflict with each other. Somebody still need to implement all of that.
I just think it makes sense that the person (or party) doing the implementation and deciding on the compromises should be the person who made the commitment.
