It should be noted that there were AAA games written in this fashion, and they were not slow. All method dispatch was virtual in UnrealScript, for example.

Well, for starters, many AAA games in Unreal had to have many core functions/classes rewritten from UnrealScript to C++ for performance reasons, where often not every call is virtual. Secondly, UnrealScript is not really a great example, since on-top of Unreal being notoriously on the slower-end of game architectures, and even Epic decided to drop UnrealScript.

And importantly, UnrealScript was designed in the 90's, when memory latencies were far less of problem.

Of course C++ is faster, although that has more to do with being compiled rather than bytecode-interpreted. But even so, we played those games on hardware that's very slow by modern standards, and it was fast enough for competitive PvP, so I wouldn't describe it as "slow" in absolute terms.