The term 'childcare' is way too broad for meaningful discussion. You need to think in terms of infant-care, toddler-care, preschooler-care, and so on. Every phase has unique tradeoffs and people tend to have more or less compatibility with each phase. For example, neither DW or I are infant types. Don't get me wrong, we love our kids and the infant phase wasn't without wonderful moments that we cherish. But overall we both found infant-care to be exhausting and boring. We made the best of it by keeping in mind that it's a phase that passes extremely quickly (amazing how quickly that time passed!). Toddler-care was less difficult for us, and preschool-care moreso.
Our kids are now in the elementary school phase and we both love, love, love, being home with the kids. No diapers or bottles, they go to the bathroom on their own and wipe their own butts, dress themselves, get their own snacks/water, and clean up and do chores around the house (still have to work with them on this last one). They also entertain themselves for long stretches (intentionally trained them on this) so DW and I don't feel like we're always 'on' with the kids. Really enjoy conversing with them, hearing their stories and ideas and love their sense of wonder, imagination, and the newness of everything. Wouldn't trade it for anything.
On the other hand, other folks we know are more into the infant phase than older kid phases. I don't really understand that (isn't the whole point of parenthood to enjoy guiding your kids to adulthood?), but to each their own I suppose.
In any case, the point is I think the question of ER and childhood depends on the intersection of the ER personality/temperament (for lack of better terms) and the life phase(s) of the kid(s) involved.
EDIT: I should add that both DW and I are ER. I suppose this helps because we share the childcare responsibilities evenly. When one is feeling overwhelmed, or bored, or just needs a break, then the other takes over.