I have no doubt that my wife or sister, who have taught elementary school, could homeschool a child. I know some parents hire former school teachers or otherwise trained teachers to homeschool their children. I also think that a proactive parent, who likely had a good education themselves, and who worked hard to learn the standards and teaching methods could do a good job.

I think the problem is that parents think that they can simply put their kid on an online course or buy books and have the child do a chapter (or some other section) a day and the child will get an education. That's simply not the case.