I think all rep ranges are important. Todays deadlift for instance was 3 sets of 5 working sets....1@RPE8, two back off sets -5%.I am now skeptical of any programs using more than 3 work sets by 5 across of squats.
For just simple training stress to build strength there's a diminishing return for most when intensity gets too high. Above RPE 8ish the curve is heading south... so we know that multiple sets of high intensity max effort work are doing more harm than good. That's not to say people shouldn't do heavy work. If prepping for a one rep max there's going to be a lot of grindy sets and singles in final preparation. A heavy single needs that preparation.
On a low intensity squat day for the next 8 weeks I will be doing 3 sets of 10 at RPE 7-9 (I use a range here because after 6 or 7 reps the fatigue is baked in and the RPE awareness is hard to settle on) which is more of a mental burn than a physical one....but it's also a way to build work capacity which will translate back to the heavy single.