That's pretty reductive, perhaps you don't have a fully connected graph of relationships in a group but other parties you do know in a group you trust to vouch for others. There's also lots of data privacy/security compliance reasons you'd want to have E2EE with large groups. I believe I heard that some larger companies wanted to investigate using MLS to encrypt internal communications, and having hundreds/thousands of people in a group where most don't know each other but they're all managed by an authority who doesn't want to be able to know what they're discussing.

I don't dislike PGP I'm just saying that it doesn't natively have PFS and PCS, which are generally accepted by security people as being necessary properties for a protocol to be considered full E2EE.