Rather we're looking for a third option. Right now it's either
accept: Maybe I don't want to take the call now, or (more commonly), it's unidentified / a scam call
decline: It might come across as rude in professional or interpersonal settings, or (more commonly) it will identify my line as being active to the scammers
What I want is an option to send it to the background, so that it can continue ringing out, while I continue with what I was doing.
I'm on android, but I guess this is a problem for iOS too