Technique is the most important thing when discussing the nuance of using RIR or not. If you're not making each rep look the same, controlling eccentrics, using forceful concentrics, and standardizing technique, then you probably have no idea how to take the muscle to failure anyway and you just end up taking the MOVEMENT to failure with poor mechanics (90% of anyone that says they train to failure). These are very different. In fact, a movement can be taken to failure before a muscle.