Nope, Netero was weaker but for sure way more experienced than his old self. He "tricked" Meruem in a fight were he had to make Netero admit defeat and that means Meruem had to kick him hard enough to make him quit but not to the point to kill him. It is like if you have to kill a spider or just break his legs without accidentally kill him, the second is way more difficult and tiresome. And by making that bet both Netero and Meruem inplicitly agreed that Meruem was on another level compared to Netero. Then even if Netero was weaker we can not say if his nen or at least his nen technique was weaker than in the past or if it has become more refined and powerfull with time. Nonetheless Netero hit him with everything he had, only the nen managed to do some damage, and despite Meruem taking the blows at full force he was almost unphased by them.
Then when Netero realized he could not win he had to swallow his pride and use the Rose. And at that point, even if Meruem was almost destroyed by it, he survived the "hit" of the nuclear weapon. And that is already a huge feat since that was tens, hundreds or even more times more powerfull than Netero cannons meaning that even if Netero was twice, thrice etc. more powerfull than what he was the result wouldn't have changed. Sure, Meruem would have took more damage but superficial irrelevant damage, that is it.