It is still in the top 15 on Twitch and top 4 on Mixer.
There is a double standard here in some ways. The Battle Royale games arguably have less content but are beloved by millions. Why is the criticism different for Sea of Thieves? Its an online only game. It has a heavy Multiplayer/Co-op focus. It also has some solo play options. It has a shit ton of cosmetics and cosmetic progression.
Also, if you look at games as a service like Destiny, The Division, RS:Siege etc...They are all almost completely overhauled from when they launched. New systems, modes, cosmetics, progression and other things have been added to those games...Granted, they all maybe had more solid content at launch, but the evidence is there for improvement on Sea of Thieves.
And also adding something as simple as a ship to ship deathmatch would give it "streaming" legs. I think criticism is valid in some areas for this game, but the ship isn't sunk...if Rare puts out a roadmap for content, and adds a couple interesting modes to the game in the short term, it could easily keep sailing. Puns intended.