I’d like to drop TAS’ ‘The Practical Joker’ into the conversation.

The simulators in the Rec Room of the 1701, seem to be a more basic holographic VR along the lines of Discovery’s combat training simulator that we saw Lorca use to put Tyler through his paces as a security officer in season one. Yet, the simulator was able to take control of the ship and advance its own objectives. It’s not as clear that sentience was achieved in The Practical Joker but it’s hard to argue that there’s no self motivation.

What the problematic Rec Room simulator in TAS has in common with the TNG holodecks is that it is integrated with the ship’s main computer. And unlike in Voyager (and Picard season three), TAS’ Rec Room simulator and the early TNG holodecks were fully integrated into and interoperable with the power supply, communications and other core systems.

I think the OP’s point that the integration of multitronic technology with highly advanced simulators may be one necessary element is fair. Combine that with access, integration and interoperability with the full resources of a starship, and it may be enough to argue that Starfleet should have considered the potential for holographic entities to attain some level of sentience.