I did mention paper/card - they have very limited value as they cost a fortune to return to most original uses, so a lot gets reused as low grade packaging. Eventually fibre length reduces to too great an extent so that they can't be recycled for ever.
Textiles are much the same - not easily recycled to original use and many are used as wipes - industry has always used recycled textile wipes. Mixed fibres are a nightmare.
Metals that are used for consumer goods are mostly extremely easy to recycle, not least because they are very easy to sort mechanically, although tin plating must produce some hassles in re-use.
As for metals being reclaimed from cullet - why not just throw the top etc. in with metal cans in the first place? The same goes for plastic tops.
Going back to glass - those of us old enough, or living in one of a very few areas in the UK where they are still used, will remember returnable glass milk bottles. In simple cost terms, glass bottles have to survive something like 6 re-uses to be cheaper than plastic, and, apparently, not a huge proportion make it that far.