In general, I would imagine it would be difficult to reach a reallllly high level of IDs without becoming knowledgeable. ( I fully recommend doing some identification if you haven’t already, to experience how much you learn ). There are exceptions though. Which this recent, somewhat contentious change tried to address. I’ve certainly come across some lower level identifiers, in the thousands, who make regular errors ( or arguably, are just following the iNaturalist identification etiquette - to “be bold” ).
Its usually worth clicking on someone’s profile in addition to looking at leaderboards. Some of the professionals do declare their experience. Though others, unfortunately, do not.
As for measures of expertise…that is an even more complex and long-debated conversation!
See here and here…and probably elsewhere too…