The amount of keys you use for osu is part of the gameplay. Changing this would lead to a completely different gameplay. It's on the same level as adding a new unit to an RTS game, or a new weapon to an FPS game, it throws off the balance and invalidates all previous replays.
At best you could have a separate play mode for more keys similar to different maps with different row amounts in IIDX; more keys will never be added for the existing game mode because that changes the entire gameplay. If this was added for an unranked or different/new standard play mode that's fine but you can't claim it's the same to play with different amounts of keys as it's not. People aren't refusing this because of "too easy" or "too hard", it's because it throws off the balance osu was built around until now.
At best you could have a separate play mode for more keys similar to different maps with different row amounts in IIDX; more keys will never be added for the existing game mode because that changes the entire gameplay. If this was added for an unranked or different/new standard play mode that's fine but you can't claim it's the same to play with different amounts of keys as it's not. People aren't refusing this because of "too easy" or "too hard", it's because it throws off the balance osu was built around until now.