Curated Blasphemer can still drop from Altars of Sorrow.

Is blasphemer a guaranteed drop?

Blasphemer Destiny 2

Unfortunately, there is no guaranteed way to make sure this particular weapon drops from these activities. This means players will have to pray to the RNG gods that their next loot drop from the Pit of Heresy dungeon or the Tier 5 Altar of Sorrows event is this Destiny 2 weapon.

Does altar of sorrow always drop a weapon?

Unlike Escalation Protocol which resets ever week, Altars of Sorrow offers a new gun every day.