Cargo ships are OP as hell. Each one is basically a hanging gardens. So, yes, naval play is way strong.
I however avoid island maps due to them being luck based. Get iron = win, Don't get iron = lose(No Frigates)
Iron IS crucial to Renaissance naval power, but there are other ways to get iron. You're telling me you regularly can't deal with lack of iron by:
1. Settling a city on iron (even if 1-tile snow island or whatever)
2. Allying CS with iron and protecting said CS
3. Trading with a player for iron
4. Allying (and signing a defensive pact) with another (honorable) player since you have no iron
5. SPAMMING privateers
6. Ultra-fortifying your coastal cities with cannon and arty (ignoring navy until the Oil era)
7. Deciding to build your cities inland once you find out have have no iron in Classical, thus making them impervious to coastal attack
8. Paying for (or getting a player to gift you) their frigates+the iron (done this a few times myself)
9. Conquering an enemy city that has iron with a surprise invasion
...Civ 5 is a game of overwhelming options.
I'm assuming you're playing MP in the above suggestions since Archipelago with the AI is kind of a joke.