Lego Dreamzzz is a great addition to Lego's TV series. It's definitely got some slow points (particularly in the first season) but overall the show has good dynamics and really fun characters.
I think it's better than some of the other Lego series that only lasted a couple seasons, mostly because I think this one has more space to grow for the future, the dream realm creates endless opportunity for new villains and fun worlds to explore.
Probably my favorite aspect of this series are the main characters; canonically younger than most of the other Lego show protagonists they can act a bit goofier and it feels natural-and while I felt that the overall character arcs in the first season left a bit to be desired, season two definitely made up for that.
The cast does a great job, especially as the show progresses.
My biggest issues are in regards to the villains and some of the plot line inconsistencies, I am writing this prior to the release of season three, and so far I think we've seen a lot of wasted potential with the lead villains, so I'd be really excited to see a more serious/clever villain for the upcoming season.
Overall I think it's a fun show and has lots of potential to become one of Lego's beloved series.