I personally don't believe receptors desensitize, we just get acclimated to the dosages, training, and food over time.
I could very well be wrong though and welcome evidence otherwise.
I have been on and off since 1989 and on consistently since about 2010, but usually at lower dosages. I never liked running a lot, despite people saying one must.
In all those decades I have never, ever stopped training hard and eating right. I have turned all the dials up and down and up and down, but never off.
When I came back to compete in my late 40s I made gains again, mostly because I focused on consistent progression. My offseason dosages were usually about 600mg and maybe 900 for a short time.
In prep of course things go higher, but that's preservation and not growth.
The only thing that did not respond to my satisfaction was my legs, and there is some evidence that we should expect this with age. My chest wasn't as strong as it was in my youth, but my back was better at 48 than 22.
What I think was key was I never went real high with dosages, leaving me someplace to go. When I was younger I never went as high as 900, probably more 4-500. All the PEDs were pharma, so it would take a lot more oil to hit today's UG dosages.
Now as I prepare to compete again it is one last blast at 1.2g and I have gone from 98kg to 105 at the same conditioning. Every workout I progress and I eat to support my progress.
With age you will hit limitations, but can still make progress. But with PEDs I think if you maxed out early you have little overhead to exploit.
I'm not saying this is you, but it is my opinion on how and why some can continue to make gains and some cannot all other factors equalized.