It’s true that on environmental timescales, all plastic is bad. But Lego is probably the most durable and reusable use of plastic for entertainment we have today.

Whatever logic brought you to the conclusion that reselling a thing means it’s no longer wanted is completely backwards. The fact you are seeing tons of Lego for sale online is because it’s so damn desired and valuable. Landfills are not filled with Lego. They’re filled with textiles from the fast-fashion industry and single-use plastics.