The main lesson from unix that is getting lost is composability of systems.

So many silos and proprietary "cloud" systems, so much glue that needs to be constantly rewritten because there isn't any stability in an ecosystem composed of competing rather than cooperating actors.

There are great things that have come along, I would say k8s has been very successful at introducing a highly interoperable, composable API for abstracting over a bunch of machines.

But the trend towards hosted services that are incentivized to create lock-in and data-gravity isn't great.