I agree that it is a design change, but in many cases it can be a good design change (with good quality). I'm proud of some of the modifications I've done to get around a poor mechanical design. Living with the original failure (however small) is not an option for me.

So I do agree that before attempting a modification, you should fully understand the problem you're trying to resolve, and convince yourself that you're resolving a design flaw. Case in point:

Nascar: Garage scoop kicks the ball straight down the middle.
Black Knight: Ball shot to upper lock flies out the other side.

My workarounds to these problems haven't had any negative side effects. They are also temporary and easily removed if someone prefers the original design.

But I agree that sometimes the right answer is "play better!".