Still, I’ve been wondering. I’ve come to learn that plastic recycling is largely a myth/scam, but what about glass and metal recycling?

They recycle fine but they still need a lot of energy to be recycled. Energy is the main issue here: energy needs to be extracted/produced which has a huge environmental cost (even solar/wind turbines have an environmental cost, as well as has their maintenance). So, the best thing we can do, as consumers, everyone of us at our humble level, in our everyday live, would be to consume as little as we can of everything. To create less waste, we should buy less, which would also mean we would need to waste less energy, a lot less, to recycle whatever can be.