I had the same problem last year, re-indexing all the files fixed it for me[1].
That being said, macOS was definitely more snappy back on Catalina, which was the first version I had so I can't vouch for Snow Leopard. Each update after Catalina felt gradually worse and from what i heard Tahoe feels like the last nail in the coffin.
I hope the UX team will deliver a more polished, expressive and minimal design next time.
Catalina and Mojave were the closest releases in terms of quality that we got to Snow Leopard. Catalina in particular since it was the release that removed more 32-bit cruft (like Snow Leopard before it).
That being said, macOS was definitely more snappy back on Catalina, which was the first version I had so I can't vouch for Snow Leopard. Each update after Catalina felt gradually worse and from what i heard Tahoe feels like the last nail in the coffin.
I hope the UX team will deliver a more polished, expressive and minimal design next time.
[1] - https://support.apple.com/en-us/102321