I think it is unlikely to end well if one partner is actively against having children. I imagine it does work out ok in the end, with both parents being active, engaged and loving parents once the child arrives and the relationship working out just fine. But in my experience that is not the case, resentment sets in and it’s not “happily ever after” at all.
I also agree that most “accidental” pregnancies are not really truly accidental. Of those I know of, a good percentage were not-so-accidental- e.g. to try and save a failing relationship/because the woman really wanted a child/another child and thought he’d come round etc. I know one was due to it being thought that one partner was infertile, so perhaps more understandable. A few have been due to less than reliable use of hormonal contraception/condoms or use of less than reliable methods (fertility tracking/withdrawal etc). I would say these are not accidental at all- it’s either ignorance or carelessness- if you chose a method of contraception whose efficacy relies on you taking it daily then you’d better make sure you take it the way you’re supposed to or it may not work, for instance. Or learn how to put in a condom properly.
Yes, no contraception is 100% but many are pretty close and the difference between clinically proven effectiveness and effectiveness in actual use tells us that most failures are not due to “contraceptive failures “ but due to user error. They aren’t the same thing. True contraceptive failure does happen- of course it does- but far rarer than I think most people think.
I would also say in a committed relationship it is reasonable to assume that if you have both agreed to a particular form of contraception which falls to one partner to take responsibility for, that they will reliably use it. So if it’s condoms it’s reasonable to assume your partner will use them, know how to do so and not deliberately tamper or remove them. Likewise, if it’s the pill that they will take them as they are meant to be used and will tell you if there is a reason they might not be effective (e.g. missed pill) so an alternative can be used. I think saying any man who doesn’t use a condom in a committed relationship- even one where another form of contraception has been agreed upon by both parties- is essentially agreeing to his partner to get pregnant is wrong. Yes, if it is a genuine failure (which, if contraception is used properly are rare) then it is one of those things but I think it is disingenuous to imply it’s all down to men and they should just be happy and get on with it. Obviously, with one night stands, a fling or a very new relationship then if you don’t want a pregnancy then it is only sensible to use a condom if they don’t want a pregnancy.