The eastern half of Hoenn is boring. It's just endless water routes and some boring jungle routes. RSE would have been better if it was set entirely in western Hoenn, maybe with a few extra areas.
Matter of opinion. A lot of people actually appreciate the effort that went into putting the water routes there. The undersea routes were especially enjoyable. Remove eastern Unova, and there goes one of everyone's favorite features from Hoenn. Also removed is the setting for the plot's climax (Kyogre, Groudon, and Rayquaza).