HMs are a shitty protoRPG tactic
Likely you will only use Surf, Fly, Rock Smash and Strength during the maingame, but Cut, Waterfall, Dive, Flash, Defog, Whirlpool, Rock Climb and whatever i forgot are either optional to get access into new areas or broken bridges
Gen 8 should instead let your pokemon LEARN how to use the field move by NPCs (like a Surfer, a Black Belt or a Bird Keeper) and keep the move as battle only.
Lets say you defeated the first Gym Leader, you now go to the Cut Tutor and if the pokemon can learn Cut as a move can also learn Cut as a field move, the Cut Tutor will not teach your pokemon Cut unless you have the badge and traded pokemon forget learnt field moves.
This is the only way i can see it coming back after Alola
