Git works over email; it works across folders (including remote ones); it can read/write several standalone file formats (patches, bundles, etc.) that can be sent via carrier pigeon, etc. As far as I'm aware, there are no technical problems with "push[ing] to people directly" (or likewise allowing others to pull from you).

There is a technical problem in the P2P setting, where it's not just one individual connecting to another. P2P protocols which just replicate data, like Bittorrent, can't negotiate a delta when pushing/pulling, so users have to keep pushing/pulling the entire repo. Radicle's network is smarter, allowing deltas to be calculated.

They also seem to be proposing many other things, which I'm more skeptical of; but at least that point seems valid.

I agree. However there are already plenty of frontends to git and this isn’t marketed as one of them. Perhaps intentionally because of my earlier point that there are lots of frontends already? But focusing on the p2p aspect doesn’t do any better of a job explaining what this project does.