A bit of a cynical take (on Hacker News no less) but after being in the industry for a while, my view is that the best definition of “level” is self-referential: it corresponds to the ability of a person to convince others that they are at that level. I also have a definition of what I think level should ideally represent: the marginal contribution of a person’s influence on the outcome of a company, relative to the…
Sounds a bit like the concept of "wins above replacement" as a baseball stat (https://www.mlb.com/glossary/advanced-stats/wins-above-repla...), which attempts to calculate how many fewer (or more, in the case of negative value players) a team would have if instead of a given player, they had someone producing the exact average of the league.