Yes, tires already produce microplastics but you also don't have to use processes that produce more microplastics by mixing them into a road just because you have big accumulated stores of waste plastics as potential building materials.

You can just say they are end of life and develop a reasonable storage or disposal method that does not reintroduce them into the environment as this could.

That isn't pie in the sky thinking either, there are numerous reactions and processes that allow you to do waste-to-energy with or even high intensity photo-degredation that is capable of producing syngas or even industrial grade hydrogen from this as a feedstock. With secondary scrubbers you can recapture the carbon and other waste products for sequestration.