I permanently mute my iPhone and then I added "Emergency Bypass On" ringtones on the contacts that I care about so I hear when they call no-matter-what.

Otherwise, I call back when I am available.

The incoming call alone is more of a disruption than an email, honestly.

Agreed. I finally just went with the nuclear option and blocked all calls that aren't already in my phone book. This has resulted in some missed connections and other inconvenience but I've decided the benefits are worth the downsides. More and more people I know are doing the same.

Some companies, like my dentist's office, are finally adapting and providing ways for their employees to text if there's no answer. I wish the FCC/phone cos would add some kind of 'return code' to callers who are blocked by this setting which indicates "This number only accepts calls from numbers in its phone book."