The only possible problem I could see is the older lenses maybe not being up to par for the new sensors in focus ability and IQ. I have seen results of what are ordinarily stellar lenses on the high MP sensors looking like kit lenses for Sony, Nikon and Canon and also struggling with slow focus and focus hunting! In the same breath, I have also seen some older lenses keeping par with some of the new glass, but they were used manually!
This was exactly a big concern that I had when I was in the process of making decisions about where I wanted to go next in photography; I had a lot of older Nikon lenses and I was able to determine early-on that most of them would not AF with the FTZ adapter. Aside from that, I had my doubts as to how well any of them, AF or MF, would perform on a shiny new Nikon mirrorless camera anyway. Sure, I really need AF, but setting that aside, I really wondered about what would happen if I stuck an old Nikkor lens on a Nikon Z6 or Z7 and if the resulting images would be at all satisfactory to me...... Camera body and lens technology has changed a whole lot since the 1950's, 1960's, 1970's, 1980's and 1990's..... Sure, I had some real gems, golden oldies, including the famed original 58mm Noct Nikkor, but..... I suspect that one reason Nikon brought out its new Noct as a mirrorless lens is for just that reason, that they wanted a lens that would work in dependable, stellar fashion with their new Z camera bodies.
For me the answer has been to set the past aside, let it go and move into the present and the future. Back in late 2019 I could already be pretty well assured that an established and decent range of native mirrorless lenses meant to go with a current mirrorless system would work well with the cameras in that system. Although there are other systems, I chose Sony.
And, yes, the availability of said lenses, the ones I wanted for the types of shooting I like to do, a few months ago and right now, was and still is important to me. Sorry, but I don't have two or three years to futz around with some stupid adapter and to wait while Nikon, even though I used that brand since the late 1980's and loved it for many years, gets around to releasing the native lenses that I would have wanted in their newly-developing mirrorless system of bodies and lenses. [Good luck to you guys who are waiting and (my guess) will
still be waiting beyond the end of 2021 for a couple of native macro lenses and a couple of nice long native zooms, not to mention long prime lenses from Nikon to mate with its Z system.]
IMHO the FTZ adapter is nothing more than a compromise, a sop thrown to the loyal fans and the masses to try and keep them happy during the several-years delay of developing and releasing new native lenses. My guess is that for the most part the resulting images are just not going to be the same. Native lenses really work best with native bodies. Younger, people may have that time to wait for new mirrorless lenses to trickle out from Nikon; I don't. Instead, I didn't and don't need to wait and moved on....
The way I am looking at things, my energy and time for the next however many years I can continue shooting any sort of camera and lens(es), regardless of brand, would be much better spent in enjoying the use of a current camera body and the current native lenses meant to mate with it now, not impatiently waiting for lenses delayed by a manufacturer's time frame......
I'm 75 years old; maybe if I were 45 I'd have a whole different perspective on things since I'd also have a whole lot more time to spend in enjoying my chosen hobby as the years flow by. Frankly, I seriously doubt that ten years from now I'll still be submitting photos to this site or any other and I can pretty well predict that I won't be hoisting around the Bazooka or even the 100-400mm lens; it's even possible, depending upon my physical and mental health status in ten years that I'll not be able to even be picking up a camera and taking pictures at all. Thankfully I'm doing fine right now (I'm blessed there!) and, yes, I'm taking advantage of it, as who knows what the future may bring?