I remember once sitting with the company CEO and going over my spreadsheet estimates of project timelines, sales projections, and department growth. At the end of it all I said to him that I didn't know if any of this was really worth looking at, since it was all just guesses. His response was that in the early days of the company they had tried doing things without plans, and that bad plans were much better than no…
"No plans" means exactly "by chance". Bad plans can do considerably worse than chance.
What organizations need to learn how to do (and unfortunately to this day Excel isn't particularly enabling) is sensitivity analysis.
One of my corporate parlor tricks is to render valuation spreadsheets (which are typically cashflows dependent on scenario parameters) into Matlab and giving each unknown parameter a distribution from three-point estimates (min/most likely/max). The difference between good plans and bad plans is the probability that your best valuation exceeds your WACC or the turnkey price to be paid or some such method.
People are often impressed that the difference between good and bad plans even exists.