I think the game is fine for starting off at lvl 1. It eases players into PC creation and game mechanics.
Apart from the initial ship sequence I think the party fights appropriate CR creatures for the adventure.
In terms of your companion backstory - I think it is fine at starting them at lvl 1, because 5e allows a lot of freedom with your background.
Lvl 1 Fighter is the same mechanically, even though a Fighter with the Soldier background probably would have seen more fights than a Fighter with the Anthropologist background. Hell, you can have a Knight background, trained all your life to be good in combat, and yet a Cobbler (Guild Artisan) can be as good of a fighter as you. And I am fine with that.
