Honestly I think that SoT's failure is more to do with the fact that this game is meant to be a social experience yet we do not have any way to socialize beyond the forums and Xbox Live. There is no social hub, there are no in-game tools, nothing...
Contrary to popular belief, it's clear that through the gameplay videos, dev insights, etc. that they wanted this game to really be a "shared world adventure game" like they claim it to be. But they were overly optimistic and underestimated the nature of zero-consequence free-form PvP and how people handle it in online games where they have no attachment to the game world nor any risks at stake for failing/losing.
As a result the community has become quite toxic compared to how it was during the Pioneer/Tech Alpha tests, and there are folks who legit believe that Sea of Thieves is just another PvP game; and that's what the game really has turned into until Rare adds more stuff to the game or else addresses the massive tentacled elephant in the room.
This is basically supposed to be a pseudo-sandbox experience where we create our own adventures, yet we don't have the tools to properly do so and PvP becomes the fallback in the absence of any compelling PvE content or reasons to work with other pirate ships. Rare failed in giving us really anything to work with beyond PvP and some very basic yet mega-repetitive activities with a few side distractions randomly scattered about.
It's frustrating because this game feels like it was released a year too early, and I don't know if Rare can even do enough to make it better. They horribly missed their initial mark in regards to what they wanted this game to be like, unless they in fact wanted it to devolve into just another PvP game.