This was helped by how not entering the first devil room at all guarantees that the next post-boss door that spawns will be an angel one. By Repentance, this was flipped completely: with health being made rarer and several powerful angel items like Revelation added to the pool, most playthroughs encourage going for angel rooms over devil rooms. This was changed when Booster Pack 2, while not making items guaranteed as they were in Flash Isaac, made them significantly more likely, and gave them a mechanic where the player was given up to four items and could pick one of them. Not only did devil rooms have better items on average, they tended to have items more often — angel rooms from Rebirth onward have a chance to not contain an item at all, simply having a few hearts that likely won't help a player good enough at avoiding damage to get angel/devil rooms in the first place.