That's probably true in a lot of cases for K-5. But I don't think any two people could teach a child with the same robustness as a the ~15 teachers most kids have during middle school/junior high, let alone provide things like labs, workshops, extracurriculars, etc. With high school that gap goes from big to enormous.

I've done all 3 of public/private/homeschool with my kids. My daughter's (public) HS chemistry class had exactly one lab that we couldn't do at home. The physics lab had zero. Bio is a bit harder since they had e.g. hundreds of pre-mounted slides for examples of various things. We also lack a biology major in our near-family.

For extracurriculars: there are club youth sports aplenty, a youth orchestra, band, choir and drum & bugle group. There are participate in various academic competitions (mathletes, model UN &c.). It's definitely harder since there's no "club rush" like in public school, but these things are available (and the total cost is rather less than a non-parochial private school, though subtracting out lost salary for the parent doing the teaching reverses that for the more affordable options[1])

1: It's completely possible to spend more than a private university tuition on private high schools where I live, but the ones not subsidized by the Roman Catholic Church start in the low $20,000s

This just assumes the median education for 6-12 is any good. Also, a lot of labs, workshops, and extracurriculars can be easily found elsewhere - a lot of these have groups specifically for homeschoolers.