Schnorr & Taproot will increase fungibility, but it's likely they'll mark all Bitcoin from Schnorr & Taproot (along with CoinJoin & MIxer) as suspicious/tainted coins 
That's an interesting dilemma. Ultimately, I think it's unlikely.
Taproot can make all different types of transactions look identical, including simple payments. Assuming enough of the network updates to incorporate Taproot, there will never be much certainty of proximity to CoinJoin or centralized mixer transactions.