Not these days - since instant boarding and going melee is a fine option now (it used to be risky, iirc, but they sort of made sea battles optional - I got into them the last time I played and had a good time with them though, they feel like what they were originally intending now I think) it’s more something you CAN get into if you wanted to. There is a gameplay reason to have an upgraded ship in the very end game, as it leads to one of the games several endgame paths to the credits, but it’s entirely optional and something you can just throw money at all at once in the end if you decide to look more into it when the time is right.