Well, for some value of "just works".

For example, I recently attended the IETF meeting in Montreal, which offers a by default v6-only network. My Mac worked fine, but my son's school-issued Chromebook had glitchy behavior until I switched to the network that provided v4.

Sounds like exactly the sort of thing the IETF's IPv6-only network is trying to shake out.

I went to IETF a few years ago and ran into issues on their IPv6 only network because I host some stuff from home, and my residential ISP doesn't support IPv6 at all. It made me really want to get all that fixed.