Use it or lose it
Yes, I'm talking to you, the aging table tennis player reading this article. Or the young but lazy one. You both have the ability to move when you play, but you don't do it enough. Sure, you gradually slow down as you age, and so many older players become more backhand-oriented rather than attacking with their forehand, which takes more footwork. Sure, younger players may find that if they use less footwork and simply stand at the table, they won't get caught out of position. Both of these are defensible positions. But guess what? The loss of footwork begins with a single non-use of your footwork. The more you don't use footwork, the faster you lose it, which gives you more reason not to use it, which accelerates the loss of footwork, which . . . you get the idea.
It's not just footwork. When I was younger, I liked to counterloop off the bounce, or back up way off the table to counterloop. (Strangely, I was better at the two extremes.) Now that I'm older (read: stiffer and slower), these shots are harder to pull off. So it'd be best to stop using them, right? Then they'd become even harder to do from lack of use, making it even more important that I stop using them, accelerating the loss of these shots, which . . . you get the idea.
Let me rephrase what I said above: The loss of any part of your game begins with a single non-use of it. Because you can't stop using it without a first non-use. So keep using it, even if it leads to a few short-term losses.
And if you do have any complaints about your footwork, let me tell you about the . . .
One-legged nine-year-old table tennis player