Overrated

(j'ai écrit ça en anglais pour ailleurs, flemme de traduire ^^)

Visually pleasing and somewhat engaging to follow, yet basically there isn't a single character I want to sympathize with/relate to, which made going through the series laborious. Major flaw: totally unsubtle character writing (please don't compare Dark to Stranger Things, ST is miles ahead in terms of cool characters, and its simpler plot is actually a strength, in the end). In majority, characters are either shallow-hey-I'm-just-there-to-make-the-plot-advance, conniving/manipulative creeps or basically crazy. Does it make sense they are what they are given what they have lived/are living? Maybe. Is it engaging to watch them live through the plot? No.
There were some good (but not stellar either) characters I wanted to see (Mikkel, Regina, etc). But the series gave me too little of them compared to all the others I didn't care much about.
Have the actors anything to do with that? No, they're good, no problem with them. Problem is with how characters are written.
Little goes in terms of character development (which is really a shame for a series that gives itself the opportunity to show basically all of its characters evolve over their entire life! And yet you get to see lots of characters who are douchebags as teens, and who remained douchebags as adults) and when it happens it much more seems to be there to further that super excellent plot that the series' writers must be super proud about. But if that plot means shoving down the drain everything that makes a character engaging, I say no.
Also, justifying why a character does the seemingly weird/incoherent stuff s/he does by a "it has to happen this way because the time loop must go on" does get old rapidly. And using bootstrap paradoxes as the main device to further your plot means anything can happen, as any information can come out of anywhere without it having to make sense: "at that point, it would be best that character knows about that. I know! Let's just have his future self come back in time and tell him, justifying at the same time how future self knew about that in the first place!". And it's that. all. the. time.
And, yes, OKAY, it is the point of the whole series ("the beginning is the end", etc.), I KNOW. But that doesn't make it good. What is acceptable over a 2h movie might get old over a 3-season series. Bootstrap paradox is not a super-duper plot device, it's a writer's lazy shortcut, and here pushed to the extreme! Realize that, in the past years, bootstrap paradox has only been used by movies considered bad (Cube²...) or pointlessly complicated, or as a gag to mock the device (Futurama, Spaceballs).
So kudos to the creators for embracing it forthrightly instead of sheepishly hiding it in the "hope nobody'll notice" parts of the script, but sorry the result isn't convincing: bootstrap paradox was lame before, Dark didn't improve its image. Glad it's been tried, but no.
Bottomline, this has the effect that even if you don't know who will actually end up being who's father or mother, or who's future version, you are prepared for it, you know it can/will happen all the time, which really undermines the twists scattered throughout the series. At some point, to keep going you just put your brain in "fuck it" mode and passively wait for the resolution. Not super interesting, and engaging, deep characters could have seriously mitigated that.

Tl;dr: Dark is a series I'm somewhat happy to know the plot of, but that I would rather not have invested 20 hours of my time in.

Also: I wrote that review after watching only the first season and the beginning of season 2, because guess what, my future self came to me and told me the rest of the series was about the same (and to make sure that was fair and nothing was lost in translation he even learnt German and re-watched it undubbed). See? I can justify anything with that sort of sh*t.