I haven't used Thunderbird in 10-20 years. Why does Thunderbird allow you do that, but not Gmail? My personal Gmail account has ~350 folders (labels) and ~300 filter rules. One of my previous work GSuite accounts had probably 1000-2000 labels and filters.

I migrated from Outlook to Gmail, and I found that I could process 2-4X the amount of emails as I could on Outlook. The key feature for me was the vi-key bindings in Gmail.