Reborn isnt supposed to be a cake walk like zeta/omicron is, i solo'd zeta with dragon dance kingdra it really was very easy(not even joking EVERYONE gets solo'd by it) reborn adds difficulty limiting you to pokemon so you can try new pokemon that you wouldn't normally use. just because you don't like how difficult reborn is doesn't mean others don't enjoy the difficulty. making it like zeta would make the game worse and people would call it an imitation and anyways making it as easy as zeta is would be pointless.
Comparing this game to Zeta/Omicron is kinda insulting imo, zeta introduces fakemons and fake mega's where as reborn makes things more difficult by putting in some really good field effects if you want an easy game by all means play Zeta/Omicron but it's got no replay value once you completed it your just like wow there is 8hrs wasted....