People don't buy products, they hire them for a job — find out what the job is.
Use when Use it when demographic segmentation has stopped generating insight, when you cannot explain why customers churn or convert, when entering an adjacent market, or when a roadmap has become a queue of the loudest requests with no organising logic.
Avoid when Avoid it for incremental optimisation of a well-understood product — you know the job, and reopening it is procrastination. It is weak for infrastructure and compliance work with no discretionary hiring decision. Done badly it collapses into vague poetry about customer aspirations, and 'the job' becomes whatever the loudest person already wanted, now with better rhetoric.
Score competing work on reach, impact, confidence and effort so the argument is about evidence.
Use when Use it when you have many comparable candidates competing for one team's capacity, when prioritisation has become political and you need a neutral vocabulary, or when you need to explain to stakeholders why their request did not make the cut without it being personal.
Avoid when Avoid it for work that is not discretionary — security fixes, legal obligations and keeping the service up do not get scored, they get done. It handles strategic bets badly: anything genuinely new scores low on confidence and reach by construction, so a team that follows RICE mechanically will optimise itself into small safe increments forever. It also cannot see dependencies or sequencing.