It's a circular argument that involves all areas of environment, development, education, finances, employment, health and society.
At any point in the cycle, you can find people who should have been able to access support, advice, medical treatment, psychological therapies, enhanced finances, opportunities or just, pure and simple, love, at an earlier point. And once you get to the next generation repeating the cycle, you're looking at what should have happened for their parents.
To try and break out of the cycle means identifying a breakpoint. In the 1940s, this was attempted by trying to do it all at once, as no feasible single point could be identified - the approach was From the Cradle to the Grave. Poverty, health, education, housing, employment. But it still couldn't be solved, not for everybody.
Anybody who has worked in education, health, interacted with other people or their children can see cases where there should have been support provided earlier. There is no fixed point where all energies could be poured into. But there are points at which a greater number of children can benefit for the longer term from targeted intervention - entering compulsory education, for example.
There is data to evidence the effectiveness of intervention at earlier ages based upon large study cohorts. Is this because nobody's interested at studying other groups? Is it because the money that support requires is so much that it has to be done with political will in mind? Would identifying and addressing the most pressing need as being a certain demographic result in howls of rage and a decline in popularity at the polling station? Or is it because the actual most effective and critical time to intervene is at the earlier age?
Fundamentally, to an individual, it is of little consolation when they or their loved one are falling through the gaps that the needs of the many are better met at a different time. That's not 'wrong', it's a normal human perception. But it doesn't mean campaigning on the basis of the best way to meet the needs of the many is nonsense.
The PoW is speaking of the many. Not the individual 18 year old. This doesn't make her wrong, any more than your concerns are in any way invalid.