RACI might be a good tool if you are experiencing one or more of the following dynamics and you lack the time (or support) to address these issues in other ways:
People working in a workgroup, not a team
People working together on a temporary/ad-hoc basis
New or inexperienced team members (without norms or role models, see below)
Acquisition, newly formed team, clash of work styles
Frequent changes in team membership
Forming a stable cross-functional team is difficult (some team members are not full-time, established specialist teams, etc.)
Not worth investing in team resilience (temporary team, etc.)
Large projects with lots of constraints and dependencies
Risk of "negative externalities." Team 1's work can negatively impact Team 2
Low trust or low psychological safety
Communication difficulties
"Superficial collaboration" or "token collaboration"
In situations without an established set of norms or collaboration culture
Lack of "role models" (individuals modeling effective collaboration)
Informal conflict resolution is challenging (e.g., unsafe or unsuccessful)
Incentives not aligned
Unclear team mandates and areas of ownership
Leaders are misaligned, putting pressure on groups/individuals to resolve misalignment.
When else have you found RACI effective?
I've found a working agreement to be more effective than a RACI, including in the types of situations you describe. RACI is abused in organizations with pathological or bureaucratic cultures where there's low trust, poor communication, no accountability (even if someone's name or role is given the "A"), silos, top-down micromanagement, and generally low competence.
I have experienced that RACI is sometimes unclear to teams (i.e. Responsible vs. Accountable), and it nudges the conversation to finger pointing (who was responsible for this? Hey, you were accountable).
I feel DACI (Decider or Driver or... Doer, Approver, Contributor, Informed) clarifies in less ambiguous terms what each person´s role is expected to be.
Thoughts?