In addition to the volume issue, there's the composition issue. When I was a kid, we recycled all our flint cores. Well, not quite that far back... Milk came in glass bottles, and the person who delivered the bottles of milk to our house picked up the empties to take back to the dairy. There were also steel cans for canned food and soft drinks (which eventually rusts away), and of course lots of other glass bottles. Now more and more of those kinds of things come in plastic, of which little gets recycled. And cans are often aluminum, which doesn't rust away.
Furniture was wood and fabric and (maybe) springs, with a little bit of pressboard (which was itself recycled paper and textile, usually used on the back of desks etc.). Now furniture is particleboard (made from sawdust), with lots of glue and some kind of plastic veneer if it's in a place that shows. Wood is genuinely recyclable (or re-usable as antiques!); I don't think particleboard is recyclable, although I could be wrong.
Automobiles were steel, fabric, glass and copper wire (with rubber insulation); plus of course rubber tires. Now they are those things plus a lot more plastic. Tires, both then and now, are essentially un-recyclable (although occasionally turned into artificial reefs).
I could go on, but there are probably more authoritative (= better) studies of this. But I suspect in general that we have lots less recyclable "stuff" these days than we used to.
(Replying to myself...) I should have added that back then, automobiles started recycling themselves even before you were done using them: they rusted something awful, at least where I lived (in northern US). My parents owned one car where if you were sitting in the back seat, you could watch the road go by under your feet.
When I grew up in Sweden, soda was sold in standardized glass bottles. All brands used the same bottles and they just put paper labels on. You'd return the glass bottles for a deposit, they'd take them in, remove the label, wash then and refill them. You could tell how old the glass bottle you were drinking out of was by how scratched the label was.
In the 90's, they were all replaced by PET bottles. We were told at the time that this was because the oil used in the plastic bottles was still less than the extra oil used to ship the heavy glass bottles back and forth.