Nikon's biggest competition is their own ghost.
Sure almost every new lens or camera model is an improvement, the however occurs that people seem to buy on some sort of online info, and in layman's terms that upgrade does not always, duly justify the cost. (You've been had when you try to recoup your losses on a purchase you should not have made,...... an actual mistake.)
Yes, I upgraded, numerous times, Cams and Glass. Of out of several grand that I spent over the years, 30-40%+ were wasted purchases. Other's regretful purchases. I still read the BS, but don't believe any of it, anymore. It's all over Photo forums/Reviews, Guitar forums, Car Forums. "I lie, so you will buy."
There is a Nikon lens rating site (Photography In M,) that is now rewriting old lens reviews, giving anything but truthful advise.