I felt D4 really needed an offline mode, the ability to roleplay as the lone hero against the darkness or just play some couch co-op as a smaller group. Having that big shared world makes the world seem less believable and more like a videogame which ruins the immersion.

A favourite that I still play to this day is Phantasy Star Online. It has such a wonderful simplicity to it, where the game and its mechanics don't get in the way of the fun. Whilst you can play it online on private servers I find offline solo play just as enjoyable.

You cannot do this with the originals without an emulator though which I appreciate is an abandonware grey area. Whilst Phantasy Star Portable 2 on the PSP comes pretty close its single player is a bit.... anime. Phantasy Star Zero on the DS though is well worth checking out.