When playing practice matches with much weaker players, here are two suggestions: 1) Simplify your serves so you get higher quality returns to practice against; and 2) Decide something specific you want to work on, such as forehand loop, and use your higher level technique to force rallies where you can work on those shots. For example, serve short backspin and attack any long return with your forehand. If you need blocking practice, push long to them, and block. And so on.
At the same time, you should fight to win every one of these points, given the conditions above. You can practice mental focus and hustle against any level of player. You might also want to play some matches against weaker players where you ignore the above two suggestions, just to work on your "win every point" skills, including serves and using your best game, not just what you need to work on. (You might want to do this especially before a big tournament, to focus on your general match playing skills.) Some might argue you should play every match this way, even against much weaker players, but I think you lose an opportunity to practice certain things if you do that all the time.