iNaturalist would agree with you; they explicitly say[1] it's not meant to be the primary source for your photos. Users generally fall into a couple broad camps:

1. Mostly use the mobile app, and take photos and upload observations directly from there. Local photo collection either isn't a priority or is backed up by their phone's cloud sync.

2. Mostly use inaturalist.org via a desktop browser, with either a standalone digital camera or mobile photos synced to desktop. Local filesystem (hopefully plus backups) is the source of truth.

I have been working on a desktop application[2] with a long-term goal of full bidirectional sync, and a secondary goal of offline usage. The current feature set is fairly modest and read-only, though, focusing on organizing local photos using data from iNat.

[1] https://www.inaturalist.org/pages/about

[2] https://github.com/pyinat/naturtag