I always agree with this.
It's just that, due to the various ways you mentioned, there has never been (and I assume will never be, but, who knows) an evergreen set of gf'd items that never needs to be replaced.
There have been so many item changes, ESPECIALLY since WoD's release, that the idea of twinking to avoid the gear treadmill is slowly but surely going away IMO.
Weird - on one hand, I like that somewhat, it keeps things fresh. On the other, it sucks that old enchant x is no longer relevant and wearing it holds you back.
As for the recent changes (like the ones that ruined azerite --- which make no fucking sense since BFA is required for new players and the HoA was an integral part of BFA - now reserved til 40? What? Can't it require level 10 and just scale up? anyways...) I assume more and more will be rolling out given that the entire expansion was delayed because of <insert reason here>. I assume the recently gf'd high ilevel relics will scale down or not work, the legion ilevel 50 quest items will be scaled down, the wod rare drops will be scaled down, etc.
If not, well, it REALLY sucks for people that were busy the first couple days the prepatch came out and missed their chance at a week or so of obtaining gf'd items. "Play before we recognize our error" is what twinking is more and more becoming, rather than just getting geared out.