Create tasklists with subtasks. Link task together
Make planner more as tasks in MS Project. Not as an replacement for Project, but create more details into subtask, scheduling and linking of tasks.
Henrik Veen commented
This should be extended to that a particular task can only be performed after finishing another. With notifying: "Your colleague cannot perform his task if you don't finish yours until...". Yes, applies a certain amount of pressure, but that's how it is in business. Of course, the duration of a task should be definable, otherwise it's not displayable. Pretty much as in MS Project.
To be able to create a lightweight Epic - feature - user story structure. Or at least 'feature - user story' structure in one planner board