If De Bruyne avoids injuries, which is a big if, for sure he would be one of the best Serie A players despite the age. I'm not a Napoli supporter but I have to admit that it is a great move, he can really make a difference, especially in the big matches.
Hopefully, your wish is coming true. However, kinda weird you hope your rival to be fit. Don't you wanna see Juve win the title instead of praying for Napoli's player to keep fit?
I try to be realistic and I know two things: 1) We are not good enough to compete for winning the title 2) Serie A has been declining a lot in the past years, any big name that comes to Italy is more than welcome otherwise we may really become a second-level league. And also, being honest, Napoli totally deserve to win because they have built a very good team over the years, without overspending, they found very good players in the most random leagues around the world, they are financially solid, kudos to them.
EDIT: I'll also add that the only team I really can't stand is Inter. At the end of the day if Milan, Napoli, Roma, Lazio, etc win, I don't really care but Inter, that's a different story 