In general, the more highly rated a player is, the more consistantly they will play. In general, they will tend to play a "percentage style" game and avoid making careless, flashy or "odd" shots.
You ay not win against that (higher rated) player, but you may feel you "play better" against them. They give you pace- so you do not have to create your own. You are able to anticipate their shots because they are logical from the point of view of common sense. The balls, more often than not, fall into your "comfort zone" so you feel good about your own strokes.
Against a "lesser player" with less refined/honed/normal strokes, you feel awkward because you are hitting to them with better form and, yet, they, somehow, get the ball back again and again. The mental aspect comes into play. Why can't you dominate against this player?
Meanwhile, they give you nothing to work with. You will get hundreds of balls just blocked back, looping balls, drop-shots, weird spins- most of which seem to be accidents, but accidents that keep you running, stabbing, reaching for high bouncers, low dribblers.
Now, most people think they are much better players than they really are. And if you are not the player you believe you should be, then your weaknesses will show. You will have to create your own pace- and, if your form and stamina is the least bit lacking, it will wear on you and cause self-doubt. You will find yourself hitting shots you have not practed to perfection. You may strive for too much against this "weak" opponent and errors will creep into your game. You will resent the opponents and blame them for what are really weaknesses in your own game.
My suggestion is practice against your regular hard-hitting, well-trained players, but to also practice against these "lesser" players and use them as a kind of bench-mark. When you start beating them easily, when you barely even notice their "awkward shots" and styles, when you can generate your own pace consistantly from the "junk" they send over the net-when, in fact, they they are the ones who no longer find it fun to play you-- then you will know that you have moved up a notch in your own playing skills.