It's not about the speed - the minimum requirements for Win 11 are a 1Ghz dual-core processor and 4GB of RAM- it's because of the processor generation. Not sure if there's been an official explanation, but the going consensus is that they aren't going to officially support almost anything that is susceptible to Meltdown or Spectre.
That doesn't mean Win 11 doesn't work or couldn't be installed on that hardware, they just don't officially support it.

It’s absolutely supported if you have SucureBoot and TPM 2.0 support. Sure, it’s not on the official support list but that’s probably because those features weren’t standard yet in that generation and it’s not tested and verified. It’ll still work fine though.

Also, performance is not everything. Support for certain instruction sets is usually the problem, when newer operating systems drop support for older chips. Of course that’s not it in this case, Skylake and Coffeelake are essentially identical and the latter does have official support.

Well, it‘s software ~~bloat~~backward compatibility, not for hardware.

And to be fair, that actually works quite well. Had a 20 y/o negative scanner driver that I could install relatively easily on windows 10. The first party macOS driver stopped working more than a decade ago (needs PowerPC compatibility) and the only modern third party driver software that gets it to work on Win, Mac and Linux costs 100€.

That is because they are still required to improve their software, and that means sometimes cutting off a part of their support. Especially when it comes to security.

But hey, support for hardware that is 10 years old is unfortunately still way ahead of the competition, Mac can't hold a candle.

And you could still bypass the TPM requirement with some elbow grease.

Likely the TPM chip. It is required for Windows Hello, Bitlocker, and a few other things to enhance security. Works much like a RSA token, if the code from the chip doesn't match the code on the hard drive it assumes tampering and will lock entry. The encrypted drive (Bitlocker) or the OS will require the Bitlocker recovery key to boot the OS (Decrypt the drive) and the password instead of the Face ID/ PIN/fingerprint you used to make access quicker. Most devices didn't have TPM 2.0 till recently, which is the version used by Windows 11 I believe.

If you don't encrypt said drive or attach the Microsoft accounts as they recommend anyone can grab the drive, reset the account password or just pull all your files from the drive from another OS. It's all forced security because the views/legal responsibility keeps looking at the companies to produce the products and blaming them for not securing their users instead of the users securing themselves.