RPE is literally the most popular thing in powerlifting right now, and rightly so! It makes so much sense. Rate the difficulty of your set on a sliding scale of 1-10, 10 being an absolute max and anything below RPE 6 being significantly easy.
But, despite the great value provided by the system. As with anything of value in this day and age, it is heavily abused.
When scrolling through lifting videos on Instagram (my guilty pleasure!) i see video after video of slow/sloppy squats being labeled as RPE 7 or something ridiculous. It pisses me off, the entire point of the system is to give realistic ratings to the difficulty of the set. Dropping a point or 2 on the scale,while making you appear more confident/strong is also a really short term way to manage your training.
The whole point of the RPE system is so that the athlete can adjust for fatigue during the session. If you squatted 500 at “RPE 6” and your goal for the day is to hit an RPE 8 then you would be adding until you reached that point. The issue with this is that the original rating was way too low, meaning that the 550 you might believe will be an RPE 8 is actually and RPE 10.
You might see no issue with this, but, it is supremely problematic. Over time it causes a huge level of fatigue accumulation. Additionally, it prevents success in competition, both mentally and physically.
So aim high but be realistic with your current performance, and your progress will be achieved far quicker. Remember strength has no limit!