The nature of a human being surely is an amusing thing...
1. If Gai hadn't been able to even scratch Madara with his life-sacrificing technique, then people all over the place would have been butthurt at how 8 gates was so weak and that it was hyped undeservedly...
2. Now that 8 gates did really turn out to be beast, as it was hyped from the very beginning, people complain about Madara being weak/nerfed, when clearly he is just having fun...
Kishi played very smoothly with what he did with 8 gates and Madara, but as I already said, humans such as ourselves are quite amusing: finding flaws in every possible outcome there is.