Meruem was pretty much the strongest character shown so far,by alot aswell,he and 2 of his subordinates never even got legit beat,and the 3rd one got beat by the EoS powered up main character.What that leaves us with is the fact that so far the strongest enemies are undefeated and so it wouldnt be weird to introduce weaker enemies than them and still have the "heroes" struggle.Also considering EoS Gon was on par with pre rose Meruem (or so Pitou says) it wouldnt make much sense for stronger oponents to be introduced since we would need to wait till the series is at its end for the main character to even stand a chance agaisnt a mid way villain (I am asuming this is mid-way,tbh I know nothing of how long the mangaka plans to keep HxH going) let alone the group beating an even stronger one (I think I made more confusing than it had to be but I hope you get what I mean)