@d3adst1ck I don’t know, what @SweetSandMan says does make sense.
Drew said in the last SoT news video that they have identified server merging through diving (HG/voyages/on-demand WEs) to be causing significant server instability which they are focusing on fixing. However this was kind of know since when diving first got introduced in S8 with countless bugs with the ship being uninteractable, spawning with missing pieces like no cannons or wheel and extreme stutter/rubberbanding when diving many times without sinking (15+ streaks). Yet, Rare went ahead and made a whole Season (S11) based around this rather buggy/server taxing mechanic of constantly diving, probably increasing the server strain tenfold by increasing the amount of server dive merges. They presumably did this because of the concept being so cool and with the degradation of server performance probably being accepted as a manageable side effect.
@SweetSandMan has a good suggestion. A lot of the current map could be sunset/vaulted through the usage of instances. There is no reason for the Pirates Life tall tale locations to be on the main map, it only opens up them to griefing. The sunken pearl could easily be instanced (go to a portal and then dive down to do the TT), same for the coral fortress.
The sunken kingdom is a bit trickier but the amount of locations could definitely be reduced, even half of the shrines and treasuries could be removed in order to increase server health and make way for new content to replace them.