I think they can get A LOT more people back on the bandwagon if they do these few things BEFORE they launch the server, I can personally say, for about 100 ppl that I've played with, these changes will bring them back:
1. fix speed sails ffs, they've been broken since day 1
2. add a new ship or 2
3. normalize bp drops and the crafting bonus so shit's not broken af. (i.e. if its fine, have a set percentage between 100 - 110% to drop, next tier 110-120% etc etc. if crafted with high crafting skill, you can only get it to the upper cap. Like, if bp is 107%, I can only get it to the cap of 110% if fine.)
4. make Gallys slower and have less base weight, this will force players to put some points into weight instead of all into dmg and resistance. The Gally meta sucked so bad. it wasn't fun. like driving a bus, but you had to do it.
5. Make Brigs 15% faster. Those boats are made for fasted paced pvp and have good maneuverability.
6. add a combat timer that doesn't let you enter the Freeport for 15 mins if recently pvp dmg'd. Freeport running IS A BIG ISSUE. ARK has a mod for ORP that works like this. Use it.
7. Make it so leveling up isn't so hard for new players. it's hard especially once bigger companies start settling and spamming all of the big islands. If you don't have the numbers or connections like we did, you're never going to level up, which makes it IMPOSSIBLE to defend your island. Instead of having to visit every island to raise your cap, why not just big POIs, the bosses, and participating in community activities (like the pvp arena I mention below for example).
All of the points above are relatively quick implements. If you want players back, then make MEANINGFUL changes. Don't just shuffle the map and call it good, or it won't work out well.
This point is going to be an ongoing project, but it still needs to be addressed... WE NEED CONTENT. NOT GRIND. stop replacing content with grindy shit to do. It's hard enough getting all of these bps, then finding all the mats for them, especially for small tribes. It was hard for bigger tribes even. I'm saying this as someone who ran a 75 active pvp company.
add more content. make this shit less grindy. add stuff that's like in other mmos like actual dungeons, player pvp arena (even for pve), and other stuff like that. hell, even ark has cool "dungeons".
There's some much more you could add to this list, but in my opinion, this is the LEAST you can do to win back people.