People defend the show because others tend to be overly critical or have unrealistic expectations. We have more knowledge of the characters and project a lot of what we read in the books into the show. GRRM has been writing these books since the 90s. The show writers have months to write the episodes. Every change they make out of necessity creates a butterfly effect. Whether that be eliminating characters, creating new characters, merging characters, or eliminating storylines. These changes push the show away from the books.

The facts is that for the show to be successful, they have to keep the characters that are known to the viewers important. One of the keys to this is to keep at least 2 characters that people are familiar with on screen at all possible times. This is why we have Jaime and Bronn going to Dorne (Elaria would be the only known character there), changing the Kindly man to Jaqen to pair with Arya, and Varys and Tyrion in Essos. The second part of this is to give them an important task in the overall arc to drive the story. This is so that the show isn't relying on Elaria and a bunch of new characters to drive the Dorne plot and Yara and a bunch of new characters to drive the plot in the Iron Islands.

We complain about plot holes and characters acting "acting out of character" but I can forgive it because they don't have the episode time to effectively show the viewers how these characters think or the writing time to make sure you cover every minor plot hole before you have to start filming them (see Maggy the Frog telling Cersei she would have 3 kids but Cersei talked about her son that died in the first season).