This game has always been considered way worse than the first, and I can 100% see where everyone comes from. But I actually really enjoyed Below Zero for several reasons, and *almost* liked it better than the first.
Pros:
Firstly, this is a pretty unpopular opinion, but I really enjoy the smaller map size and the biomes in it. Although it took away the dread and fear from the original Subnautica, it's a very beautifully detailed map and you get very comfortable with it quickly due to the size.
Second, I enjoy the story better than the first because it goes into great detail and is really interesting. The ending scene is what blew my mind the most.
Third, the basebuilding is OUTSTANDING. Unknown Worlds added tons of new base parts and you can make your base look amazing.
Lastly, I *love* the Seatruck. It's no Cyclops, but the modules are so freaking cool and I love being able to cozy up in it while driving through the sea.
Cons:
I know I said I loved the map earlier, but the good about it is also the bad. Below Zero has wayyyy less horror than the first game and really the only things in the game that can give you that panic are the Shadow Leviathans, (which are only in one biome anyway), the Ice Worms, and, (maybe), the Squid Shark. Everything else on the map seems too calm and comfortable which is the complete opposite of the first game. It's a pretty big downgrade to take away the horror element in an almost-horror game, so I'm going to take a star away for that.
TLDR: It definitely has a lot of bad because of the non-horror elements and doesn't live up to the first, but I really enjoy playing BZ from time to time and it's still a super solid game.
If this ends up still being the worst entry after Subnautica 3 comes out, then that just proves this is a damn good series.