A few minutes ago, checking my notifications, I found several regarding IDs I had made two years ago for other observers, which in turn was a year after they uploaded the observation. Nobody had touched them between then and now. Now granted, as you alluded to, these were not highly active observers – less than 1000 observations. But how long did it take some of us to catch on to being proactive and reaching out to top identifiers?
In these cases, my ID was to genus, and new IDs were to species. A year from the upload to a genus, then two more years for a species adds up to three years just for an initial species-level ID. Within the past week, I have come across uploads from three years ago, and I am the first to suggest anything narrower than family or subfamily. If the same rate continues, and another two years elapse before a third identifier comes along, that is five years+ for either an RG or a bump back to a broader level, as the case may be. It seems highly likely to me that those observers will have given up and left the platform, unless they have somehow been clued in to how to be proactive.
This is why threads like Research Collaboration: Method for supporting non-experts to label in ‘unpopular’ taxa - General - iNaturalist Community Forum are so important. No matter how you slice it, there simply aren’t enough identifiers.