Why did god allow people to be born after the fall ?

[John V]

And, if free will was always part of the plan, then God essentially rigged humans with a wild card, and then blamed us when it backfired on him. God is in every way like Victor Frankenstein. We never asked to be created. But the real kicker is that instead of taking responsibility of the fact that he created a species of unintelligible, immoral miscreants, he decided to trick us into thinking that it's all our fault we can never be good enough. He sets up this contrived and thinly veiled "test" of righteousness that he knows full well Adam and Eve would not pass, and then used the result to lay life-long blame, guilt, and shame onto all of humanity.  God is a victim blamer.

He did take responsibility - on the cross.

If some people reject that, that's their problem.