The feature is to silence unknown callers. If you know the numbers that they're calling from, you can simply add them as contacts. As a whole, I think the feature is worth the tradeoffs.

Yeah this is the complaint people often bring up, but in practice I’ve found it doesn’t matter in real world usage.

Couldn't they have left a message?

Blocking unknown is strictly better than blocking everything.

Automatically transcribed voicemails work in exceptional cases like you describe.

That's one of the things I miss most about moving from a Google Pixel to an iPhone. The Pixel was configured to use Google's call screening service, which would filter unknown callers and make them state the reason for the call. It would then ring my phone and give me the opportunity to answer or send them to voicemail. Neat.