Re ‘… is basic PPL level stuff, watch your airspeed, check your pitch attitude and monitor the engine‘.
This is often repeated under the title - Monitoring; monitor everything all of the time, which of course is impossible particularly where humans are poor monitors.
The deficiency is not knowing what the priority parameters are and how these will differ according to the situation; what to monitor and when.
Also, not knowing how to monitor - the mechanism of observing; how much deviation from the norm or closeness to an extreme, rate of change, patterns involving several displays - situation awareness.
Much of this experience can be acquired from normal operation, but it requires effort to observe, relate, and remember. This is often over shadowed by less meaning-full routine tasks - calling out the norms (but do we check), and the rarity of situations requiring intervention alerted by monitoring.
We know what is right, but less so what is a deviation, we lack a database of examples of adverse situations - to be learnt, on the job knowledge.