New to Zoho - Spam filtering seems to be awful?

New to Zoho - Spam filtering seems to be awful?

I just moved my domain email to Zoho. (Was previously hosted at Outlook.com [aka Hotmail] and before that was at Google Apps [aka G.Suite/Google for Business/WhateverTheyCallItNow.])

I'm seeing much more spam in my inbox, and many false-positives. When I was with Outlook.com, I don't recall ever having to dig through my spam folder to find an important email. But with Zoho, it's an almost-daily occurrence. (Bank one-time security tokens, newsletters from legitimate businesses, etc.)

I'm currently using the default spam-filtering settings. Is there something I need to change to make it work well? If so, why aren't the optimal settings the default settings?