There's a pretty easy solution to this. Just join grand arena, set no defenses, collect your free rewards.
Until CG stops catering to the entitled millennials this is one way of letting them know you don't really approve of grand arena and that you'll take their free stuff without any work at all. It's not like you were getting these rewards before grand arena existed anyway.
If you actually wanted to enjoy this mode I don't know what to tell you. It's clearly geared for the PvP crowd. I am also one of these people who have built there roster up for TB and not for PvP so that's the strategy I'm using. I don't care for the PvP modes so I just take the fun out of it for the other guy and they can go complain to CG forcing them to make the changes that they will ultimately make to force people to set defenses so their new, highly touted game mode will seem like a success instead of the immediate failure it's been.