There's plenty of Monero competitors, but only ZCash has an actual community and adoption. And only Grin has good tech, deserving to go toe-to-toe.
But Grin's tech is already being implemented in Litecoin so I feel like MimbleWimble coins are doomed on arrival, and Monero will remain the most popular coin of its kind.
ZCash have no community. Not on reddit not here not anywhere. ZCash have founding company with rich strong owners. They make influence so ZCash was added on all exchanges and services. But there is no community.

maybe its a sign that there is still room for competition.
I feel like most teams do not have much business experience, just because someone is a coder doesbt mean their a businessman and Monero has stopped marketing their product long ago it's just its community that keeps it going. Another new better coin can easily overtake Monero if funds are raised.