The idea behind this game is to play it instead of the original 'Pokémon Emerald', especially for those who want a vanilla experience with more features: simple difficulty modes, move splits, QOL features, new Pokémon, new areas, new rematches, and a large etc.
If you want a super difficult version of Pokémon Emerald there are already a lot of good hack-roms available. This game is not a 'difficulty hack-rom', and never will be.
Think of this as a 2.0 update for the original game. This game offers all the QOL features and improvements that I've wanted since I got my hands on the original game in 2005.
To put it simply, 'Pokémon Modern Emerald' is a modernization of the original 'Pokémon Emerald' game.