It's different when it's your own child. You see the world through their eyes and the mundane becomes interesting again. Something like tying shoes is such a feat for a kid to achieve. They are on cloud nine for a week once they learn it. This is infectious.
Some people have that feeling on a more general level. It seems I'm lucky that some of them work in the kindergarden where my two youngest kids go.
Somewhat related: while I've always cared about others after I grew up it is much stronger now. How much of it that comes from having children an how much comes from becoming a new person because of deliberate decisions I don't know.
Also probably a necessary evolutionary trait to spend the resources necessary to raise a child. If our brains didn’t reward us for child raising, our species would’ve ended 1 year after it started.
The opposite of boredom is not entertainment. The opposite of boredom is activity. Your house being on fire is not boring, but it’s also not exactly fun either.
however the same exasperating routine with someone over a long time might be described as boring. Boring is, like many things in English, a flexible concept.