That the program "pays for itself" in increased taxes implies that the additional tax burden is at least the $1-2k/month required to pay for the childcare.
So if you just cancelled the childcare and reduced the taxes you'd end up at the same place on average, except you wouldn't have non-parents subsidising childcare for parents.
Non-parents are not subsidizing parents in this scheme. And if the additional amount collected in taxes is greater than the cost of the program, then parents are subsidizing non-parents.
If you cancelled the childcare, the GDP increase would disappear, so the increase in tax revenue would disappear, and you wouldn't be able to reduce the tax rate.
If you argue that you don't want to pay now because you won't benefit in the future because you'll be dead, I assume you're not willing to support any other investments either. That sounds like you're just freeloading on the investments that our ancestors made.
From the article:
But young Canadians who were eligible for the program experienced, as teenagers, “a significant worsening in self-reported health and in life satisfaction” relative to Canadians from other provinces. So, did the Quebec child-care experiment “work”? Yes, for parents and public financing. Perhaps not for the kids.