I'm trying to exclude an entry based on the state of a lightswitch field in the entry itself. If true, exclude the entry from the feed, if false include the entry.
For anyone else who happens to land on this trying to solve your similar challenge:
Super simple - the criteria can accept a custom field value, so in my case, the criteria became
'criteria' => [ 'section' => 'caseOfTheMonth', 'type' => 'standard', 'hideFromFeed' => false, ],
What was getting in the way, in my case, was that I was fighting the Element API response cache when I was trying all my options, so I completely missed the most simple solution. That's my takeaway - manage that cache when testing!