I love this game, I really do.
I'm hooked on it, the adrenaline rush and sometimes literal anxiety it gives me was something I hadn't felt since the first time playing CSGO, and I thought that Siege was going to be more or less the same stuff with better graphics. But I was wrong.
Rainbow Six Siege has some concepts and mechanics that may have been already seen somewhere else, but every game, every match is different and that's because of the very nature of the title. And yet I want to be honest with myself, Siege is a mess in many ways... but I also think it's the greatest shooter (IN MY HONEST OPINION) of the moment.
I want to describe my love-hate relationship with my favorite and most hated multiplayer game, and what you need to know before you buy it.

You may already know where this is going. "Ubisoft strikes again", "Good job Ubi", "Ubi pls fix" is what every player thinks at least once everytime they play Siege, myself included. This studio manages to surprise me all the time, both for the right and the wrong reasons.
They created their most succesful multiplayer game ever but have a weird relationship with it.
Ubisoft has demonstrated in many ways its incompetence, from the inhuman amount of time it takes them to fix a bug (either new or present since the beta) to the way they make decisions, sometimes resulting in the complete opposite of what the community wants or thinks (see the recent experiment involving the complete removal of cross-team chat in the test servers to “combat toxicity”).
They slowly got better over time, they got more in touch with the community by listening to what players say (mostly pro players and youtubers, but in some occasions even common players) and talking directly to them on social medias.

Oh boy, where do we start. If Siege's community was a city it would definitely be Chernobyl on the 26th of April 1986, you can imagine why.
Cheaters, boosters, teamkillers, people exploiting bugs, Ddos attackers, spawnpeekers, spawn rushers, sweaty tryhards playing ranked, sweaty tryhards playing casual, terrible teammates that will try to kick you as soon as you lose a 1v3 that you alone brought down to a 1v1 (and won't even say "good job" when you save a 2v4 all by yourself on the next round), people so obsessed with their ranks they'll immediately call you copper/bronze/silver/gold trash as you kill them and won't stop bragging about their higher rank... and the report button seems useless at times. I received death threats by some salty Russian kid, whose ego was apparently destroyed after I killed him once and kept on calling me names and targeting me for the rest of the game, even after he won the game. Siege's community is incredibly toxic, and sadly no report for toxic behavior will ever change that.
It's never really a 5v5, most of the time it's a 1v9 because of all the above, and the anticheat works only in ban waves, meaning that most hackers usually get banned during the first weeks of an Operation.
There is obviously some great, skilled and friendly people out there, but all the bad stuff is so overwhelming it makes it almost impossible to find them.

It doesn't exist. Cue the 80's sitcom ending with "Wouldn't It Be Nice" playing in the background.
Jokes aside, this aspect of the game may vary every 2-3 weeks, depending on what happens during an Operation. The meta can either be stagnant for literal years or change completely within 24 hours. Let’s talk about the operators first.
Let’s say the obvious first: yes, some operators are stronger than others; yes, some operators are still, objectively, broken (or break on a daily basis because of a bug or a new exploit); yes, if you are a all aim no brain Ash/Jager main you are a disgusting degenerate very nice person.
Many operators of this game, both on Attack and Defense are overpowered because of their loadout or their ability in general. If you know the game well you know who the usual suspects are, but if I had the generalize, I would start from those ops whose ability/gadget affects the entirety of the enemy team or their own team, and other operators whose gadgets, in terms of difficulty/efficiency, are completely disrupting for the game balance. A recent example could be Clash, a very troublesome operator that at the time of writing this review is currently disabled while the developers try to fix a bug that allows her to shoot through her shield (note, this is the second time this has happened and since her release in Autumn 2018 she has been unplayable for almost 3 months in total).
Playing the game becomes extremely frustrating when Dokkaebi makes your phone ring while you are hiding or you step on a Gu Mine (which are semi-invisible, make a loud noise when they explode, keep you from jumping/sprinting/planting the defuser, poison you and damage you over time AND can be seen through walls by the Lesion who put them there). This is just a small example of what can happen during a round.
Some operators have become infamous because of how well they can execute certain strategies (mostly mercilessly rushing towards the objective killing everything on their path or killing every incoming attacker from a window with a bit of aim and an ACOG). There is a literal placebo effect around them, meaning that even if you have never played them, you are going to bust heads simply because you convince yourself that you are going to win with that operator.
Guns are an important part of Siege, some can even be considered game-changers… and of course some are easily overshadowed by them. The statistics and sometimes attachments of firearms change every season, Ubisoft is always tweaking, nerfing and buffing them, but players are usually going choose the most powerful alternative available and only choosing other guns during some particular strategies but nothing more. Shotguns, for example, are very volatile weapons and always seem to work better against you (you get sniped by a shotgun across a corridor but you can’t even kill the enemy point blank).
Note: these are the opinions of a person who tries to play the game strategically, slowly and methodically (most of the time), who mostly plays an anchor/support role and who doesn’t rush or spawnpeeks. My most used operators are:
ATK: Thatcher, Capitao, Nokk, Buck and Hibana. // DEF: Echo, Warden, Mute, Smoke, Mozzie.

Terrible. Just terrible. There is no way to know what rank or level your enemies are during a competitive match, not even their profile picture. You can either go up against someone only one rank below you or three above, but rest assure that it won’t matter, cause the ranking system is probably the worst ever created: in two words, the potential loss is twice the potential win, making it harder and harder to get back to the starting point after losing only two matches. Recently they have implemented a MMR (ELO) limit for players who queue together and whose ranks are to distant, such as Platinum 1 and Bronze 1, but that does not apply in casual matches. The ranked playlist is an unnerving, rage-inducing experience, everyone (most of the time) is super serious since their rank is at stake. As if rank mattered anyway, since it gets reset at the end of each Operation.
You can play the casual playlist, that could end up being the hardest and most frustrating match you’ll ever play or the easiest game of your life depending on how many tryhards, cheaters and smurfs you find.

What can I say, this game has seriously improved after my long, exasperated review. Of course the game has problems, LOTS of them, but I think that all in all is a game worth the experience.