Personally, I think it isn't really an improvement over Google Drive. Drive offers so many more features, an office suite, integration with many other Google services, etc.
That said, I don't think Paperless is supposed to fill all those gaps. For me, its sole job is to make scanned documents searchable (from anywhere with Tailscale) and durable (with encrypted off-site backups). Having this isolated from a Google account with already too-far-reaching access is a benefit in my opinion.
Edit: rereading the context, I think you were referring to how I used Google Drive before Paperless. In that case I just stored scans in Google Drive. I struggled to organize consistently and search was lackluster. Paperless improves on these, but also is much more hackable. It's easy to set up post ingestion scripts, backups, email ingestion, etc.
