The game is actually pretty solid. I started the game as a duo with a friend of mine without playing the tutorial so it took us a minute to properly understand what there is to do in the long run, how the HP recovery works or how we would get back his "missing" Vigil.
After only a few hours of messing around we finally figured everything out and were enjoying the game even more from there on.
But I'll go through it step by step, starting with the positives:

Maps:
The maps in this game as far as I have seen them are very good. Many things reminded me of Siege while still noticeably being focused on a PvE side and wouldn't quite work in actual PvP, so I really like that part.

Gameplay:
It's pretty solid overall. Grab some of your favorite operators with sometimes slightly modified for PvE but still their original abilities and uses, gun down some mutants either super stealthy with style or in a wild rush.
Most of the random 3 missions you get when starting a match are pretty alright and don't feel out of place. Like you would expect to do these things if you are on a mission like that.
The monsters you fight on these missions come in many different shapes and forms. However all of them have certain weak spots which makes you kill them with a single shot of a silenced pistol. If you miss a shot and hit normal body parts you have just a few more quick shots before they alarm all nearby monsters and then you get from a stealthy mission into a wild battle that is still pretty easy to deal with most of the time, but sometimes there are certain surprised that can have a chance of taking you down if you don't pay attention. So while remaining somewhat stealthy is rather optional, it still can be recommended if you want to get through as fast and clean as possible.

Studies:
Every region has their own studies you need to perform in order to progress in the overall game and unlock more maps/operators. In the first few maps in New York City almost all of them are like an extended tutorial that carries through the actual game, giving you tasks of things you may not know yet or very simple tasks that you usually can complete in a single match.
I think only 2 studies took me more than 1-2 matches because of bad RNG. The study was to kill a certain amount of Striker and all monsters on the entire map were those explosive hunchbacks.
Still got through it rather quickly and unlocked almost of the content just with the first region except for one set of operators.

And that is pretty much it. Which immediately brings me to the negatives:

The game is missing something and that is content.
While there are studies that give you something to keep in mind while you keep doing the same couple missions over and over again just on different maps, most of them are not fun and rather feel like they are a bit late into the game to force you to perform some basic actions like using the communication wheel or ping something. The missions themselves become repetitive after a certain amount and after just a couple of them you have already seen every part of the map so there is nothing too exciting to see there either.
I feel like the game needs more things to do and more so it doesn't feel too repetitive too quick. There are 12 maps I believe which is a decent amount but for those 12 maps that you have to play at least 80 times (assuming you want the achievements of 20 games per region) and maybe more if you don't manage to finish all studies within those 80 matches, there are just not enough missions and enemies.
There is a pool of 13 different missions. That is only 13 objectives that randomly repeat over and over. One of which is only a thing on a specific map if one of your operators died there without being rescued by a partner. So effectively there are only 12 missions for those 12 maps that you have to play around 80 times, not including possible failure, missing out on studies or other things like certain places to interact with.
It gets a bit worse that there aren't even a lot of enemy types to face. Most of the time you face the same 3-4 variations of monsters with an occasional stronger one in the mix.
So overall it can get quite repetitive if you play too much of it at once.
As long as you only play a little bit here and there it doesn't get too repetitive too quick so you can actually enjoy more of the game but that is only to counteract a lackluster gameplay design.

It is a pretty solid base that has a potential to be pretty fun, but it needs more variety to become a good game.
As of now it feels more like a new PvE game mode added to Siege instead of being its own independent game that it is supposed to be.

Just recently got to finish this game (finally) and I had a very good time with it.
Rift Apart brings a whole new spin to the franchise and adds very cool ideas to the gameplay which positively effects the overall experience.
The variety on weapons is very nice, bringing back so many weapons from the last title on PS4 and adding so many new, that you can play the game pretty much like you want to.
Rivet is a super cool character that we hopefully can see again if they choose to make this a trilogy.
The world design is phenomenal and really lets you look around and just enjoy what you get to see.
Combining these awesome looking worlds with an alternative dimension that you can and sometimes have to use to not just have it be a simple "Go from A to B and activate bolt" and instead make it almost like a small puzzle that helps the gameplay not to be too straight forward.

Even though I didn't plan to do so, I ended up looking for all the collectibles, as I just had too much fun in the process. I wanted to figure out how the level 5 version of my weapons would end up being so I did those as well, started a New Game+ just because I wanted to get more out of the game and I luckily was able to.
The second playthrough then got me a couple level 10 Omega weapons and I was pretty happy with my save state at that point so I closed the game very happy and satisfied and can't wait for a third title!

I was super flashed by this game from the first second.
You can explore so much and find enemies, NPCs, items and secret all over this giant map, that is even bigger than it seems.
And when you think you've got it all you watch a video of someone playing it and they find yet another cave with a boss and some items in it.
Absolutely astonishing what they have built there.
Even gameplay wise this is probably my favorite FromSoftware game so far.