Ah, I see your confusion- one of them is a year, comet. The others are 3 days.I guess. It’s only the XP/level effects that have been changed, so it’s only really a nerf if your group was actually using XP. And most of the altered effects are like, advantage/disadvantage on all d20 tests for a year, or something similar. Which is far from an insignificant effect.
If the levels are within 1 or 2, can work. Too far apart and something like a sleep spell can take the low levels out while ignoring the higher. Almost any AOE spell that does damage can put a low level at risk while leaving the high levels with lots of HP left. Burning Hands vs a 3,3,3,1 party will probably kill the 1 while leaving the 3s slightly singed.
One advantage of 1e is that due to the variable XP curve, low levels catch up fairly fast.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.