Essay:Most election systems are basically the same
The U.S. system of having an elected executive with veto power, and a gerrymandered legislative, is similar to a proportional representation system. Even if we don't have proportional representation, the third parties have an impact by potentially drawing votes away from the major party candidates unless they make concessions. If we don't let third parties run in the general, then they just run in the primary and can pull the major party candidates in that direction (like how Sanders pulled Hillary in that direction).
Even gerrymandering turned out not to be a big deal in Virginia. Gerrymandering spreads out the dominant's party's voters among a bunch of districts, making them vulnerable to getting swept in a wave election. In contrast, when they pack the other party's voters into a few districts, that party has fewer seats but those districts end up being strongholds that won't get swept in a wave election. Therefore, the party doesn't have to devote a lot of resources to defending those seats.
At any rate, even if the legislative districts are gerrymandered, the chief executive is elected by the statewide popular vote in gubernatorial elections.