That depends on your definition of "tricky". If you mean something that requires human intelligence, I would say it's the complete opposite. More or less the first thing pilots start doing during an emergency is to follow lists, it's all very procedural and most failures have been predicted in advance, as well as what would need to be done to resolve them, or at least eliminate the immediate threat -- and if these procedures do not help, you are in a very bad place anyway. There are exceptions, of course.[1] I would say that the "tricky parts", as always, are very generally the situations that we did not predict and did not program for.

[1]: https://www.youtube.com/watch?v=099cHWSbAL8

There is one benefit of having people in the loop in that they come with a completely independent set of sensors for flying the aircraft. Look at the recent issues where the single sensor on the Boeing Maxs crash the aircraft. They're far from perfect for sure though(see the times people did the opposite and ignored the correct sensors causing a crash) but there's a definite benefit to having two completely different systems monitoring the data. It's unusual to see that level of safety differentiation, not only having multiple copies of a sensor to take measurements but multiple different designs and types of sensors measuring the same thing to avoid correlated failures.

> the single sensor

And this is the problem. We wouldn't have autonomous aircraft without sensor redundancies. Even pilots have multiple redundant instruments.

Having multiple instances of the same type of sensor doesn't necessary help a lot because they tend to have highly correlated failure modes. A human pilot contains entirely different sensor hardware which, although unreliable, tends to fail in different ways.

The tricky part is not decision making, but sensory awareness.