While easier, more accessible contraception would help, it wouldn't curb the reproduction of the most irresponsible people - those who don't think this stuff through at all, religious fanatics who believe God demands that they have more children whether or not they can support them etc.

In the short term such groups are pretty minor in Western societies in the long term we are all dead.

It depends on which kind of religious fanatics we are talking about. Mormons, Ultra orthodox Jews and Amish on average seem to take good material care of their children, setting them in a middle class trajectory with few if any starving and many of them assimilating as productive secular members into wider society. As long as society as a whole reaches a favourable equilibrium with enough of them assimilating this might not be a long term problem either.