But one's vote is never for whatever the vote winning party actually does.

Eg one might like one party's position on the environment, but disagree with regards to their military position - it is not possible to find a party that represents how one feels on a multitude of issues. And even if you did agree with all a party's positions, parties change their positions - saying one thing and doing another.

And it has always been thus. One votes for a representative, who then votes on the specifics.