“A specific variant of this that has derailed the majority of work roadmaps I’ve looked at is treating people as interchangeable, as if it doesn’t matter who is doing what, as if individuals don’t matter.”
Roadmaps assign “two heads for three quarters” and pretend the names don’t matter. Everyone in the room knows which engineer ships and which one never does. Finance budgets in heads, so a manager cannot trade three average hires for two great ones. The spreadsheet wins and the project slips.