Why do I think it ignores reality? For one, we Catholics are known for having larger families in the eyes of the world. If the parents must tag-team for as long as there is a baby or toddler, then there will be years where the family do not attend Mass as a family. There's a family in my parish where the mother is currently pregnant with child number fourteen. Telling them to tag-team or telling her to stay home to care for the youngest means they wouldn't have attended Mass as a family for roughly 20 years, which surely isn't ideal. Instead, they are there daily - a beautiful sight.
Tag-teaming also assumes there are multiple Masses accessible, and at times that are conducive to one parent driving home before the other leaves. While that would be possible for us, it isn't for many. Even if it is possible time-wise, rising fuel costs could make that cost-prohibitive for many. Also cost-prohibitive for many is hiring a sitter for Sundays, which also causes someone else to do unnecessary work on Sunday.
Suggesting a mother can attend without her baby ignores the realities of breastfeeding and separation anxiety. Breastfeeding is regulated by supply and demand, which requires feeding on cue instead of scheduling feeds. While going a couple of hours might sound like a short time, if the child needs to nurse then he should be fed. Using a bottle is not the answer, either, as it can interfere with the milk supply (some can successfully do this, but definitely not all). Breastfeeding just isn't meant to work like that, though. I know that few in Western society are truly familiar with the mechanics of breastfeeding, so I know the people suggesting this aren't aware of the effects such a suggestion could have.
Even were these things feasible for my family, I personally wouldn't do it. For me, it is important that we go to Mass as a family. During the week the kids and I go daily whenever possible. They may not be old enough to be required to attend yet, but they are learning (brag: Kieran sang "Tantum Ergo Sacramentum" at Benediction before Mass Friday). Ok, so Leo rushes the altar whenever my attention is diverted, but he will learn. And we all get graces, which helps me be a better mum. I think we'll keep doing it as we are.