I think just the opposite. The removal of Zcash and Monero from centralized exchange pairs does not necessarily mean that they will lose value; On the contrary, I think they will gain more value. In fact, I believe that the two coins I mentioned should never have been available for trading on centralized exchanges, since its essence is totally opposite to centralization, but as we already know, business is business.
As I write these lines Monero and Zcash have not lost value, they are gaining it, you can see CMC or any similar website. If at some point privacy coins lose value, it will not only be the fault of the market itself, but centralized exchanges will also be responsible. These types of projects should never have been available on centralized exchanges, their place is the DEX.