The easy answer is the game numbers don’t support it and servers would feel lifeless which kills most of the drive to do anything in the game. Not to mention, these Pirates most likely would’ve gotten away with the loot regardless if you don’t learn how to defend yourself. Especially from larger ships. Stay out of their broadside, stay distant to make them burn supplies, and search for things like kegs, island cannons, and other weapons which keep your ship safe while jeopardizing your attacker’s.
Also, an observation; noticing a pattern among players asking for fewer safer seas restrictions or balanced crew size servers:
I spent [LARGE AMOUNT OF TIME} collecting [LARGE PILE OF LOOT or UNUSUAL LOOT PIECE], then got sunk by [SWEATY PIRATE CREW] before I could [GOAL]
This can be avoided by maximizing your productivity and minimizing the time you spend in one place. You don’t need 4 hours to find the loot items you’re looking for, you need 30 minutes with at worst, bad RNG. I’m not trying to say “skill issue har har har”, because any other ship that isn’t yourself being in the Roar usually means they are hunting ships with an emissary flag, or they happened to be there doing something similar. In my experience, these two events are VERY RARE.
Don’t let some clever thieves discourage you from your goal. Switch servers and try again, as your odds of succeeding are vastly higher than failure. Unfortunate situations like these happen sometimes.