That's the problem with ignore Limbo.
It's difficult to accept that God would condemn to eternal torment an unbaptized babies or someone what followed the natural law written in their consciences but they didn't have the chance to know God and the Church, for example virtuous Americans before the arrival of the Europeans. But if we accept that unbaptized babies and virtuous pagans who didn't have the opportunity to know God would be in a place where, although they don't have perfect happiness because they don't have beatific vision, they have a kind of natural happiness, it's different.
This is what people don't understand about salvation. Salvation, defined as entry into the Kingdom of Heaven, into the Beatific Vision, is not owed to anyone, nor is human nature even capable of it without a special gift from God to elevate human nature above its intrinsic capabilities. That is why the infants in Limbo do not suffer, since they are not lacking anything that is required for the perfection of their nature. It's like animals do not suffer for their lack of intellectual capabilities, since they basically have no idea what they're even missing.
Another problem that leads to EENS denial is a false notion of Hell, this idea of a single monolithic cauldron of fire, where a noble savage who perhaps gave his life to save his family is burning in Hell right next to mass murderers like Joe Stalin. We see people around us who have natural virtue and goodness, so people have trouble imagining them in the torments of Hell. One of the EENS definitions states that each individual suffers in Hell to the extent of their sins. I hold that some who lived lives of natural virtue suffer very little, and I believe that there are those who can approximate or even reach the same state as infants in Limbo. There are in fact probably some Native Americans existing in some "Happy Hunting Ground". So the view of Heaven and Hell being just binary states, where you're either happy beyond words or in an extreme cauldron of torment has actually done a lot to inspire the rejection of EENS dogma.