This is what you get when a programmer designs a system.

The end user wants to be able to just pick up a computer from Best Buy and have it work, out of the box.

Microsoft can't even conceptualize why you would want to run anything but the Windows that came with the machine. If the expected Windows kernel and files aren't there, or have been altered, that is evidence of malicious tampering—malware that must be stopped. (I'm deliberately steelmanning their perspective here.)

Streaming services want a secure content path. Game vendors want protection against cheating. In order to comply with local/regional/national laws, web sites need you to verify your age, and they need to know your computer is not lying (remote attestation). Nobody wants to be hacked.

The incentives for everyone else besides techies align against techies getting to run arbitrary code on their devices. The Secure Boot system is working precisely as designed.