Glitchy, too much going on at the same time, no useful instructions on the mechanics of what you're supposed to do. No end goals, it's basically a farming simulator and it gets very boring very quickly. Levelling up your boats is pretty much an impossibility given what you have to achieve, unless you plough real world money into it. I've spent more time searching Google for how to do things in this game than actually playing it
Generally, it's just crap considering how long Ubisoft took to make it. Sea of Thieves is far better and Black Flag, which was out before they even started on this is so superior.
Update - New season released and it's now even more of a grind. In game currency is impossible to obtain, the weapons and armour have been nerfed rendering the boss kills impossible and limiting the materials required to now enhance weapons. It's literally now a pay to play game where the only way to advance is to spend real money on it. Ubisoft are obviously looking to limit the amount of players of this terrible game, and rightly so because it's crap.