As a preface, I am fully aware that the manga for Sidonia
came out before Titan
Knights of Sidonia is one of the worst things I've ever watched. It's also one of the most entertaining. The show is desperately awful garbage for three interrelated reasons:
1. It looks terrible.
The anime is completely computer-generated and has the appearance of a circa-2008 MMORPG run on a PC with a dying internet connection. For reasons I dare not attempt to comprehend, the show has what I can only describe as severe framerate issues. Characters are deep in the uncanny valley, jerking and bobbing like corpses on strings.
2. It's impossible to relate to or care about anyone.
Not only does the cast resemble ineptly-piloted marionettes, but they have backstories and motivations which defy conventional thinking. Most of the characters (and there are a lot of them crammed into a paltry 12 episodes) are explicitly identified as being expendable. They're interchangeable, nigh-identical cogs devoid of all but the most basic character traits ("coward", "duplicitous asshole", etc). Most are clones (not a spoiler past the first episode) and conduct "photosynthesis" despite being pale-skinned and living on a ship apparently illuminated by massive fluorescent lights. Dozens of people are introduced and then immediately killed, for zero emotional impact. It's moronic, and brings me to my third point-
3. The plot is incomprehensible nonsense.
Hardly anything that happens in the show has a rational explanation. There are a half-dozen random subplots going on at any given point and none have any payoff. It doesn't help that the show constantly uses jargon never translated in the English subs. The good people of Sidonia appear to be only vaguely cognizant of their own mission. Thousands die on multiple occasions and are casually forgotten by the next episode.
All that said, this show is definitely worth watching. It's a laughably bad trainwreck from start to finish. I recommend bringing a friend and some beer. You'll likely need both.