I believe the majority of people do see the potential in Sea of Thieves for a great pirate game. It currently has the most beautiful water in any game to date, the network code seems solid, the ship mechanics seem solid, and the world (map) is plenty big for a starting point. However, I agree with what I believe to be most in that there need to be a lot of things added, or expanded and adjusted:

Higher quality and more realistic graphics (besides the water, obviously):

The caricaturish cartoon style is fine, but it needs to be tightened up to be somewhat more realistic -- thinking how Disney portrayed the pirates in the original Peter Pan animated film. Objects and weapons for some reason 'feel' like they have a low poly count, but it's really just the overly cartoony style, which needs to be reigned in somewhat to make objects have more realistic details on them (thinking the compass, sword, spyglass, etc.), as well as have characters be more realistic in appearance, while still allowing for caricature forms if desired.

Better / refined mechanics:

The movement feels clunky, like the most primitive form of movement you might see in an Unreal or Unity tutorial on creating a controllable player object. The movement needs a lot of nuances added - coming to a halt, tripping/tumbling/sliding when going down steep rocks or embankments, head bob, etc. Look at Planetside 2 for an example of what this game needs, a game that I feel has some of the best and most nuanced movement in any FPS.

A proper character creator:

A big complaint is that you cannot create the character you want to be -- you have to hit a randomizer and hope for someone who approximates what you want to play as. There are plenty of MMO games that offer better character building options, even under the limitations of a MMO type of game where you need to be able to load every unique character model into memory. If we could have an editor as intuitive and detailed as Bloodborne, that would be truly great, but even having just a wider variety of premade character templates (both attractive and less so) would be fantastic, as well as the ability to save certain profiles for later reference (also a la Bloodborne).

More detailed sword combat:

Sword combat should be an important and satisfying element in an open world pirate game, but it is very bland and shallow right now. It needs refinement -- the charging attack is too clunky and unreliable. More variety in the animations, more visceral detail when the swords clash or a would is caused, something at least as involving as the original Thief on PC had.

More detailed combat period:

Bullets from the pistol and sniper need more detailed physics modeling, you should be able to see your sniper shot sail out and start dropping slightly, with a visceral feedback on hitting something - a sharp crack and see it bounce off, as it hits the side of a ship or other solid object - a satisfying 'thunk' or similar with a small blood bloom or similar if it hits a soft target. (again thinking Planetside 2 weapon physics, handling, and feedback).

More weapons and items:

Slingshots
Knives (thrown or wielded)
Short Swords
Long Swords
Axes
Birds of prey, or parrots, that you can launch from your shoulder to circle above and randomly attack enemies for a time before they return to you.
Bombs


Different varieties of pistols, rifles, and all of the above, all with different ranges, loading speeds, accuracy, reliability (mis-fire rate), rarity, and cost. Not to mention some variance in both model and appearance (texture). And none of this tied to any micro transaction BS, maybe not even purchasable at a store (or at least then very expensive), but maybe randomly found in crates, sunken ships, and other places as you explore the islands. Also, perhaps special weapons, items, clothes dropped off certain 'notorious' mobs that you can find randomly (thinking FFXI).

[need to go to sleep]

In short, there are lots of ways to expand and refine this game and make it much more compelling to explore and fight. I haven't even touched on how they might change the quest systems and handling of PvP combat, or on adding more NPC enemy varieties, including autonomous NPC pirates and ships. It's a lot to add to the game at this stage, so I doubt we'll see much of the above, even if RARE does take any of these directions, within the next year or two, by which point, I'm guessing that many if not most who bought into the game will no longer be playing. It's kind of sad.