@frannee Working together works for us, in roughly 4 hour segments. Then we finish the day with something enjoyable- meal out, concert, movie, visit with friends.

When my resident accumulator resisted, I simply chose an overloaded set of storage shelves and took everything off, laying everything out on a table and the adjacent floor. With the "evidence" in front of us, we could see old things of no current/future use - into the garbage or recycling. Examples -boxes, bags, old paint, cords from long ago electronics, old monitors, batteries, triplicates of things like painting trays...
The remainder was sorted logically into clear, covered, and labeled boxes - no random torn up cardboard boxes or messy piles.
Then into the garage same tactic - 15 different kinds of parts sorters, many with empty drawers or duplicate screws, nails, nuts, small electronics... Consolidated to 6, the remainder donated or tossed, depending on condition. Old automotive chemicals, tools, filters (for long-gone cars and tools) were ditched, the rest placed on a single accessible shelf. The same with tubs and boxes of electrical, plumbing, - 3 more shelves emptied. Scrap metal sold or recycled...
The collections are still there, but we agreed on a "one in two out" rule. They must reside within an agreed upon space. The same applies to my many art, sewing and hobby things - if they don't have a home in their room, in totes or shelves, something must go.

Joint belongings - New luggage? The old must go. Ditto with glassware, kitchen wares and pans, etc.

It helps that we have a very worthy cause where we can donate much of our excess once a year. We have a dedicated space where all items going out are stored (way out of sight.) With months while it is still on hand, if it isn't needed there is far less angst in letting go.

This is not a once-and-done deal, as we age, the stuff we need, want and appreciate change.

As for knick-knacks, when I had a bad shoulder followed by surgery, he had to dust everything - lots of stuff no longer "needs" to be on display.🙃