What through-deck cruisers would be without Sea Harrier

Without the Harrier, would the through-deck cruisers have been only helicopter carriers?

Yes; Harrier was what gave them a practical fixed-wing carrier role.

Without Harrier, the through-deck cruisers would have been limited to helicopter-carrier duties. Fixed-wing Sea Harriers transformed the same hulls into light aircraft carriers with fleet air-defence and strike potential.