This is my future too. She made token noises about clearing up and downsizing in her 50s-60s as her aging mother was stuck in an unsuitable old house until she died at 90. Did nothing practical about it and is now mid-80s and stuck in her own unsuitable, deteriorating old house.
We now have inherited fine china sitting there unused for 20+ years since it was moved in. DF's stuff is still untouched 30+ years after he died.
I have a full house, so I will only be able to accomodate a carefully chosen range of small items. We've already got bits and pieces from MiL. Fortunately she was fairly minimalist.
DM was a war child. While she was very young, her early memories are of the war years including being bombed out. The affect on her father who saw active service had traumatic repurcussions on the family in the years after the war. Aside from the trauma which is a common cause of hoarding disorder, there was the rationing and "waste not want not" messaging.
Abundance didn't come until the 1980s, and she just wasn't mentally equipped to deal with it. She also wasn't equipped to teach me how to be organised and tidy; these are skills I've been working on in adulthood. I wasn't allowed to clear out items from long-grown older relatives, didn't have appropriate storage from the random ramshackle ancient or aquired furniture. The house still contains "doom" bags of stuff gathered up in panic tidies. Logically, the stuff in them is decades old and should all be junk now, but because there is no organisation there, there could end up being items (most likely documents) of use caught up in them. Any attempts to clear out fashion magazines from 30 years ago will be met with protests such as "I haven't read the horroscope yet"
Daytime TV doesn't help with endless shit like Bargain Hunt feeding misguided notions of value for retro collectables/ crap. Or endless scaremongering about fraud and scams (she won't let any paperwork with an address on leave the house because she's convinced that will result in her identity being stolen)
The value of stuff dwindles because either it goes out of fashion or deteriorates if stored poorly. Collectables only have value when they're matched with people prepared to pay that value. To anyone else it's worthless.
At the weekend I went to a place with garden centres, craft village, ceramics type place and thought that it is substantially filled with crap targeted at older people. Younger generations tend to be more minimalist or at least more selective about what they buy in. DH and I went down the buying general purpose crockery rather than the "for best" route unlike our older relatives and most people of our age have done the same. Partly storage space, partly just wanting to use the nice stuff rather than it being on standby for 360 days of the year.
I haven't even got to the grief and dealing with it stage yet, but it is a concern and the amount of stuff and broken furniture is a barrier to our relationship. Travelling to go somewhere where you can't even sit down because the sofa collapsed some time around the millenium is not enticing.
When the time comes, I suspect that the best strategy will be to pick through and try to find the important bits (most likely in DM's room) and let a clearance company deal with the rest.