It's a sandbox MMO, though. How do you propose to "keep" player progress on some other server that is more permanent? Especially when so much of that progress is in structures built, particularly quality of those structures? Sure, I can think of methods to do so, quite easily I might add, but not in a way that isn't disruptive to the location the character is getting moved to. Space is as much a commodity in a game like Haven as the virtual iron dug out of the virtual ground.
And then, much like PoE... does anyone bother playing in the "old world"? If GGG has their numbers right (and they should), it's a small percentage of the players that actually play in Standard leagues. That doesn't even make sense in Haven when the player population is well under 10k at best. We can see how many people are playing legacy.
I do get your desire for more permanence to the world. I completely agree with you. I'm tired of the world resets, base establishment is probably the worst part of the game to me, and is entirely the reason I quit playing so many of those private shard survival games--constantly having to start over from scratch or spawn in with a bunch of randos with an established base that are OCD about how the game "should be played."