Getting to the point where we’re going to need phone, email, and SMS to be deny all by default. Can’t reach me unless you’re information is already in my contacts.
Possibly, but we can't do that either. What we need is some balance of both worlds. OOH, we do actually need to be contactable. OTOH, being too contactable means spam. I doubt there's a perfect balance, but either extreme come with too many problems. Email has decent spam filtering, and I think that kind of cat-mouse system will persist. That said, there's "room" for more whitelisting.
In principle, "pay me a small fee if you're not on my list, if I put you on my list now it's free" would work well (optionally refund someone who contacts you out of the blue that you approve of), but there's a lot of both engineering and social details between where we are now and such a system.
It doesn't take much cost friction to deter mass spamming. I don't think much problem would be left behind from the handful of overconfident spammers who think that they can bust the odds and it's worth 25 cents a message or something.