Many of the changes were made to make for 'good TV'. That part is really debatable, as it didn't make the show better, but detracted from a really great story.
They say if they do Season 2, it'll be 'The Wishsong of Shannara'.
The problem is, they're planning on using the same actors. They're doing away with the generational aspect of it and having the mains do the story for years to come. They say people get attached to characters and tune in to watch them. Personally, I think if they do that, the book lovers will be even more harsh than they are now.
It's going to get a lot worse if it continues.