I think the level gallery with its highscores and fun statistics is really what keeps the singleplayer experience going. However, it would be even better if the location/clonemaster of the level was mentioned in the level statistics as well. This would make it easier to 'look-up' a level where you want to improve your highscore, without going through all the clonemasters to find it.
A different solution would be to add an easier way to navigate to the level gallery in the game itself. E.g.: add a list of completed levels in the Stats of a player (or somewhere else), sorted alphabetically and making it able to quickly go to a specific map.