If you think about this in terms of public policy, it gets awkward. A man wears a condom to have sex and says he doesn't want a baby. The condom breaks. If the law does not require him to support the child he fathered, then essentially the woman is forced to choose either (a) to support the child alone or (b) abort the child. So what you are proposing is essentially a situation where BOTH parties used contraception, but ONLY the woman ever bears the burden of contraception failure, and a situation that highly encourages, maybe even coercively encourages, women to get abortions if the pregnancy was unplanned (and let's remember, before contraception, most pregnancies were unplanned. Unplanned was the historical default, not the exception). That is very unequal.
So essentially, you are contorting the nature of the situation so as to ignore pertinent facts, in other words you're very selectively looking at a tiny part of the situation so you can whine that it's unequal for the poor men. But in reality, it's the woman who is more burdened, no matter what happens: whether she (A) has the baby, (B) aborts the baby, or (C) gives up the baby for adoption. In each of those situations, the man suffers less. Let's take situation A. If she has the baby, yes he has to pay a small amount of child maintenance, but as we've seen from so many threads here, it's she who gives up her freedom, pays most of the costs of raising the child, etc. His burden is far less than hers. Let's take situation B. If she aborts the baby, all he sees is that the baby is gone. La la la, he goes back to his normal life, hardly even noticed someone was pregnant. She has to make the wrenching decision, has to endure an abortion, maybe it's against her conscience, maybe her social group will judge her, maybe she will have medical secondary issues from the abortion, etc. Totally unequal, her burden is greater. Let's take situation C. She gives up the baby for adoption. She still undergoes an entire pregnancy. She probably bonds with her baby in utero. She has to separate from her baby, which may be emotionally wrenching. Many women who gave up babies for adoption never quite got over it. What does the man do: oh it's taken care of, he never meets the baby, never thinks of it again, may not even remember he once got a woman pregnant. Again, totally unequal, his burden is far less.
So as you can see, in all those situations, the burden on the woman is greater than on the man no matter which option she chooses. But you are narrowing down the field of view so that all you can see is the effect on the man, and pretending that's the only important part of the picture and the rest of it doesn't exist or doesn't matter.
Look, it's very simple. All contraception has a failure rate. Anyone who uses contraception, accepts by default that there is a chance his partner will become pregnant. All the contraception accomplishes is to REDUCE that rate. If he wishes to 100% avoid that, the only 100% effective method is abstinence. if he doesn't want to pay for any baby that results from sex, saying "But I wore a condom" is not a valid defense. It's not the woman's obligation to indemnify him from the failure rate of contraception. It's not a woman's obligation to take the unfair nature of pregnancy and endure that the resulting burdens always fall on herself so that an unplanned pregnancy never makes a man sad.