Given that the level cap is a security mechanism not allowing cheap play, like overleveling, there are no legitimate arguments against it. The price of common candies is small and should remain that way. They exist in the unfortunate event of overleveling by accident. They do not make the game easy. They just let you try again if you do not like the abuse of soft-reset.
People try Reborn because somebody told them that it is a difficult game. There is no reason to mash the "a" button as you go through. People give you important information, and that's not the old guy in a cape, where you have to solve mysteries to approach. All the necessary info you need is provided to you, right in the beginning of the story, in and right outside of the Grand Hall. By disregarding them you have to find out on your own, or have a hard time dealing with certain problems you shouldn't have in the first place. It doesn't hurt to go back and talk to the npcs. Sometimes they even say something different if you proceed enough in the story, and that's there to help you.
Now coming back to the leveling issue. Overleveling good pokemon and not being able to bring them down again is a problem. Not a problem on the player's side but on the game's side, as disobedient pokemon during a gym battle is what most people call "fake difficulty" and Reborn prizes itself for being hard because it's logical, not due to bullcrap reasons. This is why "that's Reborn for you" is a legitimate argument and should be treated as one (of course given the appropriate explanation). Increasing the common candy price is cheap difficulty no matter how you look at things