@Steve, that's great, I love the way you bring a bit of extra ratio into the discussion. And by that I mean not primarily the discussion between the people here in the community as the discussion here seems to be pretty rational anyway. What I mean are the little devils and angels jumping around in someone's head while struggling with this kind of decision
... and it can be applied right away to all other "problems" of this kind. It all comes back to your question "What are the problems that the new stuff is solving for you ?" and I would add "Is solving this problem worth the financial effort involved or is there an altenative with a better price/performance ratio ?".
Being a technocratic person - to a certain extent - I always start thinking about all these nice things and of course it would be fun to jump to a Z7 II with the holy glass trinity because of staying at the front line and because of the insane IQ you can get and the corner to corner sharpaness and to have the headroom for shooting the 70-200 2.8S with the TC20 and ... and ... and ... not even thinking about video (yet).
On the other hand I had to shoot some photos of my car the other day when I suddenly realized that I couldn't even remember when I had my 70-200 mounted to one of my bodies the last time. It didn't feel good to discover that obviously the "equipment and technology devil" made me buy something in the past that I actually use so rarely in the end that I could ask myself why I bought it in the first place.
If I calculate realistically the entire cost of switching to another system and the hours I have to work for getting the money, IMHO I think I am better off spending this time - well, part of it to be honest - with going out with the gear I have, have fun, enjoy being in company of mother nature and wait what the future might bring.
Also there are other doors opening up, especially at the lower end of the sophistication scala, because the drop in price level for used DSLRs and lenses is becoming more and more significant. As a consequence hobbyists and enthusiasts being on a budget can now get hands on equipment, that they wouldn't have been able to afford a couple of years ago, and thus have a chance to take a decent step forward with theier photography without turing everything upside down on the gear front.
Sometime even a step backwards in public opinion can mean the right step forward for you personally and this also applies to photography gear.
For sure there are a lot of people out there that wouldn't be able to bring home a shot like you did with a D7200, even if you give them a Z9 and a 600 f4 S plus TC-20 and a 2000$ tripod with titanium flex shooter, shooting 500 frames an afternoon with top notch 14 fps
.