Dalmatia and Ragusa should be Croatian. 'nuff said.
But no... Really... They were parts of Croatia since time immemorial!
I don't know what your sources are, but you should re-consider your knowledge of history of the Adriatic.
The Avars settled there in century VII, whereas croats only got there a century after.
That being said, coastal dalmatia has always been a mixture of morlaks and latinized illyrians, and neither of them are croats.
Morlaks are tied to the latin world due to their language, which is what got them to be "friends" with the venetians, that bought the whole coast in the year 1437.
As a matter of fact the dalmatians and romance speaking cities of the coast considered the croatians to be their "enemies" up until a very late date. Even under Hungarian and croat occupation, the dalmatians (which served as the famous venetian "oltremarini" and "schiavoni" in the republican army) were left indipendent, up to the point where they could have their own alliances.
They were, on top of that, of great importance in most of the venetian battles against the turks, serving both as ports and as manpower to fend off the turk, as the hellenic did in the Aegean.
The dalmatian communities of the Adriatic looked at Venice as queen of the Adriatic, most of the time also paying Venice with gold and silk to get their benevolence. Famous is the example of Arbe, which used to pay 2 kg of gold and 5 kg of silk to Venice, each year. Most of them just supplied Venice with manpower.
Even before renaissance, due to their ties with the latin world and Venice, the dalmatian language in places such as Zara had already been replaced by veneto.
To this day morlaks are almost extinct and so are most of the latin populations of the eastern side of the Adriatic, due to Tito's ethnic cleansing in the 1900s.
Most of them moved to either Romania or Veneto, meddling in with the population.
Ragusa was NEVER Dubrovnik.