The problem is reality.

I've found that Finance, and the Tax Office of any government, rarely care about your Agile processes. They have their yearly cycles, and C-Level will always want to follow _those_ cycles.

Then, for those that have schoolgoing kids or work with people that have schoolgoing kids (aka: everyone everywhere): there is the school vacations cycles.

These too rarely care about your scrum rituals or PI planning. This means that your calendar is not a reflection of reality: July/August barely exists. Same goes for November or December. And at the same time December is full of actual deadlines due to end-of-year financial cycles.

And finally: the complexity of the work itself rarely lends itself to the linear timelines people expect.

Rarely have I met a Product-person, or a SCRUM person, that actually understands this. And can account for it in their Agile way of working.

End result: a continuous stream of disappointment. What fun times we live in.

Then don't use it in those environments. Agile is not a silver bullet, nothing is.