RACI is a simple tool for a common problem: unclear ownership. For each significant task or decision, it names the one person Accountable (the buck stops with them), who is Responsible for doing the work, who must be Consulted, and who is only Informed.
Its value is in the conversation as much as the grid. Filling one in usually surfaces the tasks that everyone assumed someone else owned. Use it where clarity is missing, not everywhere for its own sake.