Yes, it is possible to be too deliberate. Take it too far and you risk becoming too scripted, too inflexible in the face of changing information/environment, or ignoring new (sometimes better) opportunities and ideas.
It’s better to be deliberate in planning (goal, desired benefits, activities) and flexible in execution.
Take it from much (much much) smarter minds than mine:
“The best strategy is a balance between having a deliberate one, and a flexible, or emergent strategy” - Clayton Christensen
“Truly successful decision making relies on a balance between the deliberate and instinctive thinking” - Malcolm Gladwell
The bad news: As always, striking the balance is easier said than done.
The good news: You can deliberately build flexibility into your plan. Here are some examples:
Build Voice of X (customer, user, analyst, etc.) activities and analysis into specific points of your review process
Test assumptions and concepts early and often
Kick off projects that are benefit-driven (or as Dr. Christensen says satisfy a “job to be done”) that allow the team to explore many potential solutions
Develop modular presentation decks that can be amended or navigated on the fly – depending on the audience’s needs at that point in time
Prepare responses for potential audience objections – that are only used when necessary
Have multiple methods to frame your ideas to fit the situation or personality of the audience
Does this help? I'd love to hear your thoughts.