TL/DR: The griefing issue would be worse without pvp. You want to play an 'rpg' with cosmetics as the end game without pvp? go play destiny.
Having played many games throughout the years I have played games that have given the option for non-pvp servers. Here's the 'shocker'... Griefing. Still. Happens. In fact, many times it is worse. Let me introduce you to Sea of Thieves non-pvp:
- people still camp outpost to turn in your hard earned loot while you can do nothing to stop them
- people will gladly stop by an island that you are stopped at in hopes of stealing your loot while, you guessed it, you can do nothing about it
- And, here is the kicker about this, if you get a griefer on your hands following you around the seas, literally the only two things you can do about it is scuttle and hope they don't find you again or quit the game and rejoin and hope its a different server.
The dynamic of the game becomes worse in a pve only sort of world. It just doesn't work. The fact that in SoT they don't give rewards for killing other players or sinking other ships is a testament to the fact that the dynamics of the game were thought through. The reward for pvp is fun and a little bit of potential. You might find that one person that has a lot of loot for grabs in several hours of game play, but for the most part, the progression is slower.
The best advice that I can give besides a blanket "get good, bro" is keep your head on a swivel and, for the love of god, stop trying to use a sloop like a galleon in a fight against a galleon; use your maneuverability, make cut backs, circle islands, you CAN survive even a persistent galleon crew by playing smart. Yes it is annoyingly obnoxious and takes 10x longer but at least being ABLE to fight them off is way more beneficial than not.
