Those grievances he mentioned seem to have nothing to do with the end of the game.

https://www.forbes.com/sites/insertcoin/2018/03/21/xbox-ones-sea-of-thieves-is-no-more-than-10-of-a-finished-game/#707cebfc26be

Xbox One's 'Sea Of Thieves' Is No More Than 10% Of A Finished Game

"Sea of Thieves having No Man’s Sky’s strengths and weaknesses were warranted."

"The problem is that Sea of Thieves is not a complete game. It just isn’t. It’s maybe 5 or 10% of one, but given what other open world/co-op games can offer you for $60, it’s just astonishing how little Sea of Thieves offers. The issues? Where to start.

• All three factions feel the same with nearly identical, radiant fetch quests that have you go to X island to get X thing and return without sinking/dying. Raids are just some waves of skeletons.
• The islands are almost entirely lifeless. You can see them all in about a day of play, and they almost never house anything interesting other than your quest objective, however pretty they may be.
• Enemy variety is almost non-existent, skeletons, snakes and an "endgame boss" kraken that has already been turned into a meme by players, as the thing is just tentacles with no actual body lurking under the water. Perhaps a metaphor for the entire game.
• Progression is almost entirely cosmetic short of a couple new weapons and items. And while you can change your ship’s sails and paint, there are fundamentally still only two kinds of ships in this entire pirate game, which seems crazy.
• PvP is a poorly thought-through griefing nightmare. Other players almost always attack on sight, derailing your quests or just being flat out annoying. My last three quests in a row, I went to turn in a chest and came back to find that someone had stolen my empty ship for literally no reason other than to be irritating. The last time, someone called me a "c***" on their mic as I tried to swim after my departing ship, and then shot me in the head. Good times. It’s The Division where the entire map is the Dark Zone, and it makes it incredibly hard for players to enjoy what little PvE content there is in peace.

That’s it. I can’t even make more than five bullet points because that’s almost the entire game right there."

Those grievances he mentioned seem to have nothing to do with the end of the game.

The first and fourth do. According to Rare you receive different type of exclusive quests for Pirate Legends so if you haven't beat the game you haven't played the pirate legend quest. And Pirate Legend is tied with the progression system since it's the highest tittle in the game. So by not beating the game you haven't seen all of what the games progression system has to offer.

From the review it seems the game doesn't offer enough to be motivated enough to even go for that rank. If things only get cool after a certain time but the way there is not exciting enough someone has failed at some point.

But if you're gonna review a game Imo you should at least finish the game.

If we check metacritic no mans sky has alot of 80 's or higher like 27 of them for an extremely afwul game I expect Sea of thieves to have even more better than no mans sky like 60 something 80's or higher. It also has better content

But you also have to take into account that no mans sky was $40 and done by an indy team of 20 people. This is done by rare and cost $60 and has Microtransactions.