Generally speaking, food waste renders products un-recycleable. Even minor amounts of impurities make molten glass and molten metal totally useless.

I don't know about glass, but any junk in molten metal just burns up and the ashes can be skimmed off the top. It's not really the metal I'm talking about, it's the plastic and paper which are pointless to even have in the system.

It goes through a process. It doesn't make metal or glass useless.

Biological Treatment: Organic waste, including food waste, is often separated either at the beginning of the process through manual sorting or through processes like anaerobic digestion. In some facilities, organic waste is processed separately to produce compost or biogas.

There isn't and won't be a technology that is going to ever economically recycle (closed loop, meaning used for a similar purpose over and over) most of the plastic containers in the trash, especially when it's 40 different types of plastic all mixed together (with generous amounts of contaminants mixed in). Sure, it can sometimes be downcycled once, like shredded into some kind of filament and used to stuff a low-quality cushion or something. That's about it.

If it were economic to really recycle it, China wouldn't have stopped taking ours. And most of the rest of Asia followed suit, which is why municipalities are sheepishly hoarding it in warehouses now without a plan, or just admitting to themselves (if not their citizens) it's a sham and diverting most of those plastics we put in the blue bins straight to the landfill.

One more thing: You're right that multi-stream recycling wouldn't fix the problem for the plastics, though just collecting metal and glass and letting the plastic take a more direct route to the landfill would be more efficient and would have a chance of getting people to understand that the blue bin doesn't redeem any of their sins when it comes to plastic.