Traded-in vehicles don't go to waste. Vehicle life cycles are actually pretty efficient. If a car runs, and is street legal, it will likely be bought and used by someone. Once a vehicle does not run, it will go to a salvage yard and used for parts. After a while, whatever metals are left will be recycled.

Edit: Yes, I don't think everyone should just ditch their ICE cars to "help the environment." I don't know if anyone is arguing for that. And, all new cars are bought by wealthier people because all new cars are way too expensive and have all kinds of "features" with dubious utility. I do think this is a problem. Until a couple years ago, I've never bought a new car. The only reason I bought a new car is because I couldn't find a used car that was worth the price (used car market was pretty fucked up back then). Coincidentally, I ended buying an EV, lol (a Leaf).