Nope. All blood is correctly explained context-wise. Mega Man X introduced some new robot types: Reploids and Mechaniloids.
The first one are robots that resembles human beings: they can think, feel and make their own decisions. X, Zero, Sigma and almost all characters and bosses in the series are Reploids.
The second one are robots made to mimick other living things, such as plants, insects and animals. Basically all common enemies, and most sub-bosses, are examples of Mechaniloids.
Both Reploids and Mechaniloids are robots whose bodies evolved over the years, in order to become more and more similar to the body of the living thing they're trying to mimick. In the case of most common Reploids such as X, Zero, Sigma and most other common guards, their bodies resembles human beings to the point there's even blood flowing in the veins of Reploids (or any other red liquid that resembles blood somehow). You can see Reploids bleeeding in some anime cutscenes of Megaman X4.
Megaman Zero occurs 100 years after the events of Megaman X, and in that era, the technology involved in the creation of the bodies of Reploids and Mechaniloids are even more advanced. All the people in the Resistance Base are Reploids whose appearance resembles more humans than robots. They can even feed themselves. And of course, they bleed just like human beings. That's exactly why there's blood on these series.
All those context explains why there's blood in the series. It's not as if it's unnecessary. And yes, the argument used in those "bad reviews" is weak and ignores most of the lore introduced in Megaman X series.