Harbour defense ranges are a bit extreme

[Prophet_01]

NPC's fortify pretty much every coast they get a hold of and with the extreme range of turrets it is very easy to block routes between islands very effectively.
So unless you play very aggressively and completely dominate the NPC's, most trade routes will eventually have to pass through multiple defense bubbles to get anywhere (especially to the new world).

I've just had 2 NPC's declare war at the same time (pretty much out of the blue) and as a result that game is just lost. I lost 3 shipswithin the first minute or two and while I actually do have quite a large fleet, there is simply no way I'll be able clear my trade routes before I'll go bancrupt. I'd have to conquer 3 major islands at once to open up the most important routes.

The map feels too small and crowded for these kinds of long range defenses.

[Chompman]

When people are in a alliance together they will go to war at the same time like that.

You need to work on diplomacy to prevent that if you can otherwise you face the risk of it.

Without the range static defenses have they could be sniped outside of their range from ships with the use of certain weapons you can equip and depending on your map style it may be rough at times if you don't clear your trade routes.