There are some objective-ish criteria we can apply: plot structure, themes, language and dialog complexity etc.
There are also more subjective criteria which can nonetheless employed like character development and character complexity in general, plot lines and plot wholes, number of literary and narrative devices employed etc.
Mandalorian is a simple linear narrative with an episodic structure with a rather thin plot, little to no character development, and the only "arc" serving as the single motivation for the plot to advance.
This especially evident in Season 2 Episode 7, where they tried to cram a series worth of a character's redemption arc and world building into a single episode.
This doesn't make Mandalorian bad. It's a very enjoyable well executed show with surprisingly few really weak points. This also doesn't make Mandalorian great, or amazing.
In 14 episodes Firefly had more character development, better dialog, working jokes and better acting than 16 episodes of Mandalorian.
As to boring drivel, that's my view of Rogue One: thin plot full of plot holes. The only narrative structure in the entire film is "15 minutes of static talking heads followed by rather uninspired and badly edited CGI action"