I had a few channels setup and I was setting up a Roku Ultra from my son. We reset it, and it just loaded 90 channels I never had setup before. Now we have to waste are time cleaning this mess up.
This is NOT cool Roku. This is how you start to lose loyal customers.
I believe there is a screen during the setup up a new device/factory reset which should present you an option to not install these "recommended" channels. (Or, at least, there used to be).
May be easier to perform another factory reset and see if you are presented this option rather than trying to delete 90 channels.