If you use AEAD, you clearly expect your recipients to use a recent client. Same as if you want to use PQC or any other recent feature.

If your audience is wider, dont use AEAD but make sure to sign the data too.

With respect to the 90's design, yes, it is not pretty and it could be simpler. It is also not broken and not too difficult to understand.

You're missing my point. I agree that you can use Sequoia to communicate between peers also using Sequoia. But you're no longer compatible with the overwhelming majority of PGP deployments. So what's the point? Why not just use a modern tool with that same group of peers?