What frustrates you most about task planners and to-do apps?

I'm curious about what people actually dislike about task planners, calendars, and to-do apps.

If you use (or have tried) apps like Todoist, Notion, TickTick, Google Calendar, Microsoft To Do, etc.:

• What feature or design choice annoys you the most?
• Is there anything that makes you stop using a planner altogether?
• What do you wish task planners did differently?
• Do you prefer a simple to-do list, a calendar, or a combination of both?
• Is there anything you find unnecessarily complicated in current apps?

I'm doing a small research project about task-planning software and would really appreciate hearing about your actual experience.

There are no right or wrong answers — I'm especially interested in things that may seem small or insignificant but make a planner harder to use.

P.S. This post was written with the help of AI because my English isn't very good yet. I'm collecting information about problems people experience with task planners for my college coursework. Thank you for your understanding!