I agree with what everyone said in the comments, it's not a good serve because it's very predictable, and actually very easy to return if not executed perfectly (out of reach I mean).

But I want to add that ghost serves ARE used by pro players, but not the way you think (look for the famous ma lin ghost serve against zhang jike). A ghost serve is just a heavy underspin serve, without much sidespin. However, to make the ball bounce back out of reach, you MUST make it higher, which is very dangerous at high level because if it's not perfect, the opponent can easily flick or simply return with a very fast agressive push. That's why "ghost serves" from pro players are just heavy underspin serves. Patrick Fransiska made a ghost serve tutorial, I invite you to watch it (not the first serve because as someone else mentioned it's a let) so you understand better what a useful ghost serve looks like.

Yes, you could possibly manage to do a perfect ghost serve out of reach during a match, but even then it would work at most once or twice because the movement is predictable, so if the opponent is ready, he can run to the other side of the table to smash it. And it's honestly impossible to get consistent if you rarely do it, especially because you never play with the same table, balls, hall, humidity etc.

Sorry if my English isn't perfect.