A player who levels only DoW/M can't repair their own gear, can't make their own gear and try for HQs, and can't participate in materia-craft.

A player who levels only DoH/L can't participate in instanced raids and other battle content and can't get a personal chocobo.

A player who does both can partake in everything this game has to offer.

This is about player choice and related consequences, not discrimination.

As for the promises of the initial release of the game, people need to learn to let go after a while. This game is not following Tanaka's vision anymore, but Yoshida's vision. It's not even about which was or would have been better. It simply is what it is. First thing Yoshi P did when he was put in charge of the game is confirm with the players that they were up for drastic changes.