I agree too. I assume that state machines (SMs) are underrated because they are used in a "wrong" way which makes building them impossible: I mean most authors focus on listing and naming all the states, but in fact, they should not do that (IMO) but rather focus on events, conditions, and actions, which cause state transitions. Secondly, they should use hierarchical grouping the reduce number of edges in the state graph.

There are concepts like workflow engines and FLUX architecture which help in designing simpler SMs. For example, by limiting state transitions to events similar to how modern microservices communicate there will be less events. And actually many workflows themselves are implemented in (smaller) state machines.