iOS 14 appears to allow me only to silence unwanted calls and texts. I want to block them. How can I do that?

For SMS text spam forward the message to SPAM (7726) and your carrier will block it for you and others. But, as discussed, this won’t accomplish much because it’s easy to spoof a phone number, and there are also online services that will let anyone send a text to a phone number using short codes.

For phone calls the phone cannot block a call once it leaves the carrier’s network destined for your phone, all it can do is send it to voicemail. Some carriers offer apps that let you report calls to be blocked at the network before they get sent to your phone. AT&T Call Protect is an example. This has the same spoofed number limitation.

Just so you know it will only silence unwanted texts that come in via iMessage (blue bubble) not SMS texts (green bubble).

You can block the ones that come in from phone numbers by creating a Contact card for each one and blocking it. Since most of the robocalls usually spoof phone numbers you may inadvertently end up blocking numbers that you need to go through. And some will come in and actually appear to be a contact that you already have. Check with your cell service provider and see if they have a program for blocking, particularly for texts.

https://support.apple.com/en-us/HT201229