Two jobs that look alike
The confusion is understandable, because both jobs happen on the same grid. But a calendar's job is memory: it holds what has been agreed (the meeting, the dentist, the flight) so that two people who agreed it show up at the same time. Planning is a different act: it happens before anything is agreed, among things that have no time yet: the training that could go anywhere, the friend you keep meaning to see, the money admin nobody will ever invite you to. Deciding which of those deserve this week, and which hours they get, is the work a calendar has no mechanism for.
The tell is what each does with empty space. To a calendar, a blank Tuesday evening is free time: available, meaningless, first come first served. To a planner, that same blank space is the scarcest thing you own: the fifteen or so genuinely discretionary hours a full life leaves you, which every unscheduled hope you have is silently competing for. A tool that treats your capacity as blank space cannot help you spend it deliberately, and that is not a flaw in the calendar. It was never its job.