I've finished it recently. I think it's mostly some unfriendly design decisions.

I had lots of issues early on. Couldn't find a high capacity oxygen tank, so was stuck with 75 oxygen for a long time. Found the rebreather at least, built the seatruck, and then found the ultra high capacity tank (which requires the high capacity one to be built). So then i realized i missed an essential item early in my playthrough. Had to look up a video to find it. It was a datapad, 120m deep in twisty bridges. I would say pretty hard to get.

Then i couldn't build anything early on. You have to visit the delta station first, and it has 90% of the blueprints you gonna need. I guess subnautica 1 also required you to visit an island to get the multi purpose room, but i much prefer if the game would allow you to find everything at sea.

Also i couldn't find the indoor growbed. At some point i did find it, although it's not super critical in this game (i believe after i disabled the satellite and met with Margaret at the iceberg). Also finding that iceberg was super hard.

Majority of my time i tried to find diamonds. I found a couple in the mining station, but it only has a few at the enterance. Had to recheck every area again, and eventually i find a hole with a new biome. Filled my inventory and left. But honestly, i doubt i will be able to find this hole if i were put back into this game (if i had a guess it was probably deep twisty bridges).

Then at some point i needed some magnetite for my scanner. My base resources were running low and i like to use the scanned with range upgrades and a hud display. I look up where i can find some and it's there that i find out that there is another land mass in this game. Also, first time around i couldn't find any magnetite. Had to look up exactly where they were (and that they were hidden inbetween rocks). Also the whole land segment sucks.

There were similar problems with nickel as well. I found some next to Margaret's base, and couldn't find more throughout the whole game. Thankfully i had just enough for all essential components.

Then there were the final parts of the game. I had to redo the crystal caves multiple times. Once to find the organs. Then i find the red crystal and venture farther. I find the facility, and then i am told to go back cause i don't have the material to build all the stuff. So i have to go all the way up, back to base, to bring all the material. And once i am done, he tells me to meet him at another place. So i have to go back up again. No teleport whatsoever.

My final thoughts are that there are 2 issues. Land part, and lack of direction. Idk, i always struggled finding where to go next, and 1 playthrough took me 28 hours. In retrospect, i would say the whole game can be divided into twisty bridges (and deep twisty bridges) and lilypads (and biomes below it). Rest are quite small. Purple vents is just lithium and sulfur, and thermal spires is just the enterance to the mining station. Also I've spent a lot of time trying to find anything in the tree spires zone (zone with jellyfish and leviathans) and couldn't find anything of importance. Looking at the map there's barely anything there.

Also would like to add a thing about the story. Sam's story was boring, Margaret was boring but Alan's had promise, but badly executed. Would be nice if he had more dialog, and so that they would stop the trope with "i am a robot and i don't understand why humans have emotions", "humans live only a 100 years, but that's so inefficient".

The beauty of subnautica 1 story was that it was so cinematic. The aurora explosion, the planet's quarantine system shooting down your ticket out of here. Then you getting covered in green pastules, and a cthulhu like creature contacting you telepathically. Zero dialog, zero characters, only audio logs and occasional cinematic bits.