I dived at Papageno Resort and at Wananavu Resort. The former with a group organized by a local dive shop here, and the latter by myself as an extension. At Papageno the boat motors broke down frequently and the O rings on the tanks leaked. The AOW divers went on a separate boat to sites that the organizer told me had extremely rough water. As an OW diver I was not allowed to go with them, though from the descriptions I would not have wanted to; but another OW diver, who did want to go there, told me that the DM told her this was not true at all. I don't know.
At both places, there were no big pelagics, and what fishes and corals there were were not much different than in the Caribbean, except, as I said, I saw soft corals for the first time. That was cool. I am not an ichthyologist. I may have seen species of fishes I had not seen before, and perhaps a fish-counter who keeps a life list and gets excited by seeing a new species would have loved it. I just like pretty fishes, and those in Fiji were no prettier than those in the Caribbean.
It took me half a day to get to L.A., then about 10 1/2 hours for the flight to Nadi, where we had a 5 hour layover, then a short commuter flight to Kadavu, followed by a two-hour very rough boat ride to the resort. Call it maybe 30 hours of travel each way to see little I would not have seen in the Caribbean. Definitely not worth the travel time. (Travel is hard for me because I can neither read nor sleep on the plane. I listen to music and/or audiobooks, which gets old on a ten-hour flight. And it gets harder the older I get.) I have done a fair amount of traveling, but the older I get the less inclined I am to spend hours and hours to get somewhere. The most spectacularly beautiful place I've ever seen in my entire life is practically in my back yard; that's south-eastern British Columbia, Canada. Half a day's drive, no flying. And Belize is three flights, none of them longer than 3 hours.
The people in Fiji were very friendly and the country is beautiful. I was told (I have no independent confirmation) that the lack of anything big was because Fiji has granted fishing permits to big Japanese companies that pretty much take everything. That might just be a legend.
More adventurous people than I might have a very different experience there.