i was a big believer in training to absolute muscle failure, especially in the lower-mid rep ranges so heavy weight would be used.
really failure is just the depletion of energy and ATP, not producing enough to be able to perform another rep.
rest but about 10-20 seconds and you restore some ATP and can bang out another few reps, so have the muscles truly failed?
and without enough high rep sets we're probably not getting enough blood flow in the target muscle either.
hypertrophy is the product of progressive overload, volume, frequency and blood flow.
with low-mid rep sets to failure we're bound to hit a wall, the initial overload in weight won't last but we can still overload with volume and frequency.
i don't think training should be restricted to HIT vs volume, train to failure but not making it a staple and the be-all & end-all of training.
train in the low-mid rep ranges and high rep range, cycling volume, weight/intensity and frequency.
i train some muscles 2-3 x a week,
1 day is a mostly heavy work, reps 6-12 with a moderate amount of volume
2nd day is high reps with a lot of sets and volume, 12-20 reps, still heavy but not heavy enough for me to fail on rep 10
3rd day is the same but with a lot of partial reps/drop sets
i.e. 21's on most exercises
also, i wouldn't confuse high reps with low weight!
just because you do high reps doesn't mean you should be throwing around pink dumbells!
most of the monsters and pro's built a foundation of strength with big weight and low reps, but after that they make sure they get the reps out, high reps but with heavy weight with enough volume to achieve hypertrophy.
it's been done for generations - Arnie, Nubret, Oliva all trained like this as did the generations following like Haney etc
Dorian did more volume than people think, his prep sets which he thought of as warm-ups would be most people's work sets!
but it all added to the overall volume and stress placed on his muscles.
imo this is the best way to achieve hypertrophy.
also another example could be gymnasts, they have some of the most impressive physiques of any athletes. they train with a lot of volume and frequency but little to no failure.