Earlier quoted context omitted.
Problem is not the agile, but useless sinecure managers trying to rebrand "agile" as something in which projects don't need planning, can be completely chaotic and any requirements can be changed at anytime without affecting the deadline. "Hey we don't really need to make any decision ever or even know what we are doing. That's the great thing about agile!"
Projects tend to need substantially less planning than people think.
The management in the company didn't plan anything and the meandering development process showed it.
Please don't underplan. It's awful for morale to throw away work because of bad planning.