The resource drop rate you need to focus the engrams is abysmal unless you run bounties on all 3 characters, twisted energy is non-existent to "extend" the grind, and the umbral Engram drop rng is iffy at best. The community has spoken up to Bungie on dozens of occasions that this type of economy is Garbo, yet they keep doing it. Plus the afk forge farm (any farm that don't offer guaranteed drops in general) isn't even that good unless your RNG is on point.