It's the mindset I think you are missing T. There is going to be a clear transition and it is already happening.
The majority of collectors collect to reconnect to a younger age. Most of us poster buyers buy this paper because when we went to the theater the first thing we saw was the poster advertising the coming soon or the now playing. The younger generation has seen a flat screen tv playing a trailer or rotating a poster image and no poster at all. Movies are less of an event so there is less of a need to have a piece of the experience.
The main difference is in rom-com, comedy and drama. Everyone wants the tent poles, Potter, Bond, Marvel.
Examples from this year...
Hotel Transylvania 3 - 167mil, number 11 gross - for sure sell out 10 years ago, plenty left.
Oceans 8 - 140mill - #14 on the year - dumpster fodder
About anything after Ready Player One , #15 on the year, average interest at best. Star is Born has been decent but it is a very wide scope interest film.
If mid grade posters have lost some of their shine, it is not because of a lost love for paper (or at least not directly), but because cinema does not interest people has much as it used to. There are no movie stars anymore, no career directors to follow, no big names to watch. Too much distraction from social media, not enough time. Movies are about branding, and branding is a flash that is instantly dismissible. Except for a few rare titles, movies all look the same. Also playing a part is how quickly movies come out on ancillary markets. No wait, no trepidation, instant gratification.
You're right, there will always be a few titles that beat the effects of time, but most movies are forgotten as soon as you step out the theater. It didn't use to be like that. Names on the marquee used to mean something. Nowadays, people are more interested by Jennifer Lawrence's new fuck buddy than her work on the big screen.
So if movies don't mean anything anymore, neither do their posters. It makes sense.
Is the hobby dead? Not according to what some titles sell for, especially from the 80s, the last era before it started to go south. Like I told you privately, Dale, I see lots of title sell for x2, x5 what I paid for them. But they are the top of the crop.
I think it all comes down to the titles people remember and want to remember. Not too many of those anymore.
T