I think the problem with Nikon at the moment is two fold. Not quite having the right products for the masses right now, and a false image that they are the only company suffering with supply issues.
On the second point, supply issues, most manufacturers are suffering on new product. Nikon are suffering possibly slightly more but they are a smaller company and with new products in higher demand. The 100-400 is a particularly bad example, but it's not been out that long when you think about it. I only just got hold of the 105mc this week after waiting for stock for a long time.
The first point I think is the real problem, for me at least. I've shot Nikon for many years, both professionally and personally. But the Z bodies have been frustrating for me. The Z7ii being the best for me until the Z9 came out. It was really the AF for me that was frustrating as often I'd hit it's limits. So the Z9 arrived and I was overjoyed. The AF is there, it works exactly as I would expect. But right now I'm considering selling the Z9 and either jumping ship, or just getting a Z7ii again until the Z7iii or similar. I've found the Z9 doesn't suit me these days. I assumed I'd be ok since I used to cary a D3 with me everywhere, but these days I think I have been spoilt by the small size and weight of the Z cameras before it, and I think I've now come to the conclusion a full gripped body isn't for me. Which is now frustrating as I really only wanted the AF, I don't need the video features, only the fantastic AF. The Z9 kind of draws a lot of attention as well, which I'm not really fond of.
When you add the two things together it makes people talk about jumping to another brand because they can't get what they want. But what is acutely obvious is that moving to another brand will only fix the supply problems, if you absolutely know the brand has all the lenses and bodies in stock that you need, because if not you may end up in the same waiting situation.