Lots of young EAs are struggling with the issue of whether, when, where, and how to have kids, and whether becoming a parent will undermine being an Effective Altruist, in terms of opportunities costs such as career, time, energy, money, focus, and values.
For whatever it's worth, I'm happy to answer any questions you might have about parenting -- its pros and cons, ethics, practicalities, etc.
Background: I'm a 57-year-old dad; I've raised a 26-year-old daughter and a 6-month-old baby. I've also helped raise a teenage step-son, and I come from a big, close-knit family (I have about 30 cousins.) I've lived as a parent in the US (mostly), UK, and Australia. I'm also a psychology professor who's taught courses on parenting-relevant topics such as behavior genetics, educational psychology, evolutionary psychology, human intelligence, evolutionary game theory, and decision making. I've been involved in EA for the last 6 years, and I have a pronatalist orientation, with an interest in population ethics, reproductive bioethics, gamete donation, and cognitive and moral enhancement. I'm not an expert on every practical or scientific issue about parenting, but maybe my perspective could be useful to some EAs.
I generally agree and think that babysitting shouldn't be your only source of evidence, for reasons like what you describe. Ideally, you should use a bunch of different threads of evidence, including babysitting, getting a pet, talking to parents, research, etc.
Unfortunately, the only way to really tell is to actually do it, but that is too costly because then there's no turning back.
Two things to keep in mind though:
1 . Taking a pill to enjoy drudgery
On the "you'll feel differently when it's your own child" argument. This argument feels strange to me. Imagine some sort of drudgery you hate (e.g. filing taxes or cleaning the toilet). Imagine there's a pill that makes it feel like that's the most meaningful and enjoyable thing ever, and it will make you prioritize it over your existing values and spend millions of dollars on it and tens of thousands of hours on it for the rest of your life. People who take the pill say they love it and would never go back.
Would you take the pill?
Some people might because hey, what matters is things feeling meaningful. I wouldn't, because I don't want to add a competing goal thread in mind to compete with my current existing values, no matter how much I'd enjoy it later. (This of course doesn't address things like the learning curve you mentioned)
2. Parents give biased answers
Asking parents gives you a biased view because it's hard for parents to psychologically admit that they made a mistake, let alone tell somebody about it. It would just cause too much suffering on their part and would also make them a worse parent.
And it's more common than you think. I can't find it now, but I remember a survey I read saying that ~10% of parents regretted having children, and that's definitely an understimate, because there's such social desirability bias and most people can't even admit it to themselves.
To help counter that, I recommend checking out https://www.reddit.com/r/regretfulparents/ and watching The Letdown (a funny and as far as I can tell, decently accurate view of the downsides of being a parent).
Of course, look at both sides. You can also read Selfish Reasons to Have Kids and talk to parents.