I absolutely agree with all of this - and especially with the statement I bolded (if you'll allow me the liberty of using "bolded" as a verb).
I have striven very hard - with everything that is in me - to improve my wildlife photography over the past several years. And I believe that my work has improved dramatically over that time span. However, I have been using the same gear - the same two cameras and the same three lenses - for 3 1/2 years now, with no upgrades or additions during that time. Hence, gear is not responsible for the improvements during that time.
Yet, I often want to make images that my gear does not allow me to create . . . I do feel that the limitiations of my gear are holding me back.
So, while improving one's imagery is not necessarily linked to upgrading one's gear, there can be times when there is a correlation . . . not from an IQ standpoint, but rather from an "ability to get the shot" standpoint. Image quality is often negligible and, for many, meaningless - so for amny it is not a valid reason for upgrading gear. But, if different gear allows you to create images that express your vision -to get shots that you cannot get with your current gear - then such upgrades should not be underestimated.
For me, getting a 1.6 crop camera opened up many image-making possibilities that were closed to me previously, when I was using a 1.3 crop and a full frame camera. The crop allowed me to capture images that better matched my vision, and facilitated a tremendous "growth spurt" in my efforts to improve.
Now, if there was another piece of gear that could enable another growth spurt in my imagery, I would do whatever I could to get that new gear . . . but I don't believe such a things exists, at least not yet. That is why I have not upgraded anything in the past 3 1/2 years.
Right. And I think part of the problem in these discussions is the tacit assumption, among some folks, that upgrading only refers to image quality issues. Yes, IQ can be a legitimate reason to upgrade, particularly in regards to landscape and wildlife, where the intricate geometry and "feel" of texture itself can be a purely aesthetic value, though one that requires a fairly high technical solution or, if not, an 8X10 large format camera, to properly render, especially if large prints are involved.
But "upgrading", as you point out, can certainly refer to utility or function; for example, if you have a camera and only a 400mm lens, and now you have a job for a real estate company, you might want to seriously consider getting yourself a wide-angle lens, irrespective of IQ considerations.
Astrophotography, as we've seen today, was not possible without technical advancement, and as I frequently cite, the infamous bullet-through-the-apple shot required gear-oriented development, no doubt about it.
And for me, the ergonomics of a camera are important; it enhances the overall photographic process. Others don't care, as long as the camera gets the job done.
Also, the type of gear you use might not necessarily improve your photography, but it could change your approach, expanding one's photographic outlay while still retaining one's personal style. That is, what I would shoot with a large, bulky large format camera is going to differ from what I would shoot with a rangefinder or DSLR.
So I absolutely recognize that gear is not immaterial, that important correlations exists, but, as for the other poster, I wanted to underscore the fact that different types of photography can excel with different types of gear of all makes and quality. And for me, it was actually going 'backward' that fueled my inspiration and best facilitated my needs---I don't worry about becoming complacent in this regard. And of course, I absolutely understand that for other folks, it is a matter of going "foreword" to attain similar benefits. And then there's every thing in-between.