Crafting a plan is useful, however, there must be a provision for dealing with changing priorities. Scrum allows reprioritization after each sprint — a timebox of 2 to 4 weeks.
Timeboxing guarantees that the team has the time and peace of mind to develop a working software. This timebox is short enough to allow the product owner (in coordination with product management, business owners, project sponsor and key stakeholders) to change priorities to match business needs or in response to the result of the sprint review.
The product owner is empowered to adaptively plan… including stopping / cancelling the sprint (analogous to stopping the manufacturing production assembly line if there is a need to). Hanging on to an outdated plan is not useful.