Many players believe the only way to improve is by constantly playing against better players..

Many players think that they need to only play against better players if they want to improve their game, but that is a complete myth. Looking at the different areas, tactics— yes, against better players you can practice tactics because they put you under pressure. You can also play against lower level players and focus on your tactics, like your court position, your shot direction, trying to reduce the chaos within the game. Technically, you can practice technique against better players, but often they don't give you the opportunity because a better player will probably be trying to break your rhythm them. So technique is actually better played with a training partner or with a lower level player that is able to keep the ball under control. You will get more repetitions like that because you can lengthen the rally, whereas the better players are probably able to finish the rally off. So that technical side is great to practice with lower level players or even yourself.