Well he actually saved the show from the bad HAMMING of Gates McFadden and Marina Sirtis in the first two seasons.
When they mellowed out the show really took off.
Yes, it was the really terrible acting of the supporting cast that allowed him to shine. The worse they were, the more perfect he was.
How many characters could have been recast or even eliminated without harm to the show?
Yar - well, we know the answer to that one...
Crusher? They had another Doc for awhile and the show worked.
You could pretty much rewrite, remix, or eliminate any of the supporting cast and still have had a solid show.
We would have missed Worf, he had some excelling sodes in TNG and gave use a brute force mannlyness to the show especially when he described Klingon flirting.
We SO could have done without WES.
The others weren't so much as bad but zeros....place holders. They added to show by digits but the acting was at it's best with Picard, Data. But honestly most of us didn't watch TNG for the acting but for the good and great stories.
I was not in love with the idea of Data as a character - the inverse Spock character doomed to rationality but yearning for humanity. That said, Spiner did a good job with the character.
As for Worf, he was all bluster. He got P'wned quite a bit for such a tough warrior. He blurts that no Klingon would ever taken prisoner, but gets take prisoner more than once. He was character trapped between cultures - he didn't seem manly so much as socially constipated. You could count on him to have a primitive violent impulse in a situation, which basically demeaned his character, but even worse he was kind of neutered because he rarely got to act on those impulses.