There was a reference implementation called Amaya.[1] It died, because the set of web standards is vast and sprawling, and without a business model implementing them has been seen historically as overly expensive.
In the absence of a reference implementation, the only other suggestion for consolidation is to take an existing implementation and crown that as the winner. The problem is that implementation, regardless of open source, remains under the control of its altruistic parent company. That company then effectively gains sole control over the direction of the web, which we typically agree is a bad thing. The web is (and always has been) bigger than one engine.
In the absence of a reference implementation, the only other suggestion for consolidation is to take an existing implementation and crown that as the winner. The problem is that implementation, regardless of open source, remains under the control of its altruistic parent company. That company then effectively gains sole control over the direction of the web, which we typically agree is a bad thing. The web is (and always has been) bigger than one engine.
[1] https://en.wikipedia.org/wiki/Amaya_(web_editor)