I find subtasks are useless for managing workload/projects as it's difficult to see progress.
Creating a separate App for subtasks and linking them to the main task solves this somewhat, but it requires the use of automations to create a "template" (or at least I haven't found any other way) and it's cumbersome.
Checkists are good in that they can be assigned and progress automatically seen upon completion, but they are very limited in functionality. If time could be estimated/tracked against checklist elements and rolled-up for the main task, project/workload management would be massively improved.
Without a proper solution it's very difficult to justify moving from a pure PMS