Honestly, there is a universe in which this show could have been great and I'm disappointed it failed to live up to its potential - I'm not all that surprised about it though.
After having watched the show and seeing a lot of people bemoaning how it should have just stayed true to the source material, I decided to read the manga and see for myself. And it's... fine. It's just fine.
Sure, certain things are handled better in the manga (I think we can all agree Kaneda's weird shrine should never have made it into the script), but over all I feel the script writers made a valiant effort to expand on the source material and give the characters more depth.
Padding out a 5 chapter manga enough for an 8 x 25 minute TV runtime is no easy task but I actually think the show pulls it off pretty well, at least as far as pacing is concerned. The acting, editing, and cinematography are all extremely solid as well.
Where the series falters, however, is just about everywhere else.
The additional characters are all either completely unnecessary or ruined in some way, new sub-plots often start promising but then quickly go downhill and never quite manage to actually contribute to any character growth for our main leads.
The show adds a lot of little details to the characters and environments, but for every loving addition that gives the characters depth and makes the story more compelling, there's another addition that swings way too far the other direction and just makes things odd. It's a constant see-saw of one step forward, one step back and it gets a bit tiring after a while.
All in all this story has a very good concept which it only partially manages to make use of, but given that the source material never lived up to the potential either I personally can't bring myself to be too mad about it.
There's still a fair few things to enjoy about the show and if the synopsis interests you I suggest giving it a shot. Don't expect too much though, or you're unfortunately likely to be disappointed.