I don't think we will miss Semedo (but I also think he is a good player).
We get virtually nothing out of him going forward, which isn't good enough for a wing-back. Defensively, he is generally reliable, but a right wing-back often has plenty of cover and is rarely isolated like a right-back would be.
Semedo is obviously a much better all-round footballer than Doherty, but you could argue (quite easily) that Doherty was more effective as a RWB.
I expect Rodrigo Gomes to be much more effective as well, and I think we could find a decent alternative at a relatively low price if need be.
Concerns about losing another captain are valid, but hard to comment on his influence in that sense.