Everything after season 3 has had some serious pacing issues, but it hasn't stood out as much as in this season, where the gang is split up, several episodes are spent on not all that interesting subplots that move along at a snail's pace - and that after millions died on Earth.
Hopefully the final season will be a bit more narratively dense.
This show's concepts couldn't be more cliché if they tried. Every shot is a work of art though, so it's still worth watching. Don't expect a story beyond what you already thought of yourself when you were 12.
Season 1 was some of the best TV ever created up until the last few episodes.
Season 2 is, unfortunately, a continued drop in writing quality with no end in sight.
Better to pretend the show ended after the Season 1 finale.