We would never play differing levels ever again. Old school PC death, energy/level drain, and even Wish/Deck of Many Things level-change shenanigans, subjective individual XP awards that not everyone acquires, all of them were disruptive to the party balance, even if it is a perceived imbalance. Some PCs will forever be behind everyone else unless the DM invents some reason to close the gap. And if the DM does decide to close the gap, then the justification for entire system that allowed it in the first place was flawed. Telling someone that they will forever be behind everyone else is rough. A player and friend who has family responsibilities and can't make every session should not be punished by falling behind. Our respect for our real life relationships should matter more than the story.
As a cooperative game, the effective balance/contributions of every player is far more important than this particular illusion of verisimilitude that not everyone is equal. There are already other aspects of the game that can showcase a difference in effectiveness, whether class/subclass/species design components, min-maxing, motivation, engagement, or skill levels in reading, math, reasoning, or cunning. It's a game. At least design the mechanical aspect so that everyone in the same party has the opportunity to contribute equally at the same level.