Annoyingly, the obvious 'replacement' for pooled mining is not non-pooled mining, it's cloud mining that puts the hardware in the physical control of the pooling party. Thats a step down.

Instead we /just/ need to improve the tools so that people can pool for variance reduction without turning over their consensus controls. It's straight forward: the pool gives you a coinbase txn specification (e.g. "must pay these addresses") and you mine whatever block content you want, returning shares to the pool. Then you get low variance payout, but without handing over control.

GBT was supposed to enable it, but it was supplanted by stratum before it could get adoption.  I'm not sure of how to break out of the status quo.