Yes, there has to be a reason/ purpose for changing, because the current non mirrorless DX apsc lineup gets you so much.
I agree with the first half of the sentence.
Old saying "if it ain't broke, don't fix it."
But the second half depends on what you want/need.
If you only/primarily shoot in daylight, yes, the Nikon F-DX lenses are fine.
But in DIM light, there are only a couple F-DX lenses that will work.
And that is where I ran into problems.
There is no fast F-DX moderate wide, about 24mm.
The ONLY FAST F-DX prime that Nikon made was the 35/1.8. I had to settle for that. Something was better than nothing.
This is my fast companion to the 18-140 GP lens, as a 2-lens kit.
NO ONE makes (current production) a F-DX equivalent of the F-FX 70-200/2.8. This would be a 40-135/2.8, or close to it.
At the time I was shopping, the closest lens was the discontinued Sigma 50-150/2.8 (big and heavy).
So, for me it came down to the Nikon F-FX 24-120/4 or 70-200/4. I went with the 70-200/4.
The Tamron F-FX 35-150/2.8-4, had not yet be released. If the Tamron lens was available, I may have bought it, rather than the Nikon 70-200/4. Tamron has since discontinued that lens