That's fine but if forecasts are continually way out then there is something wrong with the assumptions. Decisions are made off these forecasts, so it is important to be close enough.
Sorry but your following the same failure to understand.
The forecasts are not continually way out. Thats the claim of those who wish to convince you to dismiss them.
Most are within acceptable margins of error. When they are not they are generally due to some kind of shock.
You cannot predict say a war breaking out, or a pandemic.
Normal professional forecasting processes will include a feedback, they analyse what caused a difference, if they could have predicted that, amend logic etc.
Also the timescale is important.
If I said to you predict next weeks shopping bill you would probbaly be able to make a decent guess, based on the last fe weeks.
What if I said I want a forecast for the next 12 months, 24 months, 10 years?
Suddenly factors become far more relevant that you can ignore for next weeks. Inflation, will there still be 2 people in your house, etc etc