This has been an ongoing problem for a while now and the answer is simple: give better incentives to PVE!
My friends and I personally have nearly stopped to PVE entirely since there is nothing of merit to get from it. I have been posting for a long time now that old time-limited cosmetics are so much better than anything they have released in the game for the past year that quite literally we no longer feel it worth to PVE. The new events don't give rewards we ever feel worth getting, and knowing they will come back now we know that even if we change our minds we can get them later.
We are all wearing what we believe to be the best cosmetics without any new cosmetics having been added to the game that we find worth getting. Most of us prefer more simple-looking cosmetics with more sleek designs over what Rare has been releasing lately especially for the ship.
Overall this game lacks any incentive for us to PVE with lackluster rewards that we have never found to be worth. So the fix is easy: 1. Add better cosmetic rewards for doing PVE 2. Make better time-limited PVE rewards so that we feel compelled to do them! We want new awesome cosmetics but most of the new ones we felt did not hit the mark quite simply.
To give an example the last cosmetic I changed personally was the dawn hunter shirt my go-to cosmetics are as follows:
Character: BlackDog Hat, Dawn Hunter Shirt, Jacket of the Dammed, Ferry Man Gloves, Black dog pants, Black dog boots, Athena eye patch, PL curse, Ferry Man Blunderbuss, Obsidian Sniper, Glitterbeard.
Ship: Insider Hull, Insider Figurehead, DA sails, magpie cannons, obsidian wheel, admiral capstan (would switch to obsidian but don't have)
Most of the cosmetics are simple and sleek to really let the other ones stand out.