The thing with difficulty is the difference in competitive experience of various players. If you would be an experienced competitive player then you would naturally see the value in many less hyped pokemon choices when the better choices are unavailable until later. Therefore you can still run through the game without much difficulty. For those players, reborn adds a variety to your pokemon experience without you having to use a lucario every game like 5th gen or ralts every game like the 6th gen games. The game is still challenging to some extent, that's the good part of reborn
For the less competitive players, they may struggle when some of the best pokemons are taken out, forcing them to take the less conventional picks, but then they discover value in new pokemon and possibly adding to their competitive experience, which is a good thing as well. The game may be frustrating at parts, but very rewarding to certain people.
Now for those without any competitive experience that run through the main game with their overlevelled Charizard every time, this is when Blaziken comes in. It's the game in easy mode, there's nothing more frustrating than retrying for the Nth time and still lose to that same gym leader. For players that want to take it easy, or just enjoy the story (admit it, you played reborn for the plot), take the easy path and then maybe when you get better you can take another starter for your 2nd run and start new discovery.
This is, how I see this matter at least...sorry about the long post