At Mediavine, we offer several optional ad units to customize your ad experience. Leaderboard ads have been around for a long time, and we do give you the option to run one if you want. Settings > Ad Settings > Optional Ad Units
However, we recommend running the Desktop Adhesion Ad instead of a leaderboard. Leaderboard ads tend to have very low viewability, which can pull down your site wide viewability score. By contrast, the Desktop Adhesion Ad is highly viewable, and more valuable to advertisers.
You can read more about leaderboard ads and their impact on viewabilty here: