I genuinely don't understand why this is so hard to tackle.

Phone numbers are a scare resource and the telecommunications networks heavily regulated with numerous central points of control.

This bullshit is scaling because the companies which gate and sell that access have no obligations, legal or otherwise, to deny scammers access to their resources.

I no longer can answer my phone. I get at least 20-40 spam/scam calls per day, and many are legitimate companies calling for loans and refinancing offers, which started after I got a home loan. I cannot seem to stop them from calling, and even though my phone number is listed in National Do Not Call Registry for many years, it hasn't worked at all. The only relief is that on my iPhone, I was able to block all calls not found in my contacts (ie whitelist phone numbers only).

Now, my only worry is that I might get a call from someone who I need to talk to, but is blocked and I won't even know it. For example, what if I get an emergency call from police/fire/hospital and I won't even know it. I also tried using "Screen unknown caller" feature, but then, no one likes them and sometimes they think it is AI bot and they usually just hang up (which is great for spam caller but not for legitimate caller)

My only solution that I could think of is to have a dedicated phone line just for friends/family/work, and a second line for banking/shopping/utilities/everything else.

T-Mobile’s Scam Shield works really well for me. But you have to get the premium tier.

One of the biggest concerns I have with phone scams is that the people most vulnerable are the elderly, and they don’t have the knowledge on how to block these calls (if a technical solution is the only option).

And further to that, the elderly are also the ones who cannot block unknown numbers, because doctors’ offices seem to have random numbers they call you from (they may have a pool of numbers but it’s not reasonable to add all of them to contacts). Blocking all unknowns would block these important health related calls as well.