I don't know many primary aged children doing chemistry practicals. Mine does, actually, because a home ed group allows older primary kids to participate, but he wouldn't be able to in school at his age.
I don't unschool because it wouldn't suit my personality - I'd stress over it too much - but the bits of unschooling we do do have, honestly, worked really well. My son has an obsession with the periodic table now, and that was completely led by him. I can't even remember how he found out it existed as a concept tbh as I'm not a scientifically minded person. We bought him a Top Trumps set with the elements and properties, and there are a ton of books on it that are child friendly - one is a coffee table book, of all things, with the most beautiful photos, and grouped facts for every element. For a 9 year old, that's ideal.
A good teacher will try to teach to an interest the kids share - that's why they theme learning in a term to eg Harry Potter, Dr Who, the World Cup etc. If you only have one child to worry about then you can allow them to follow an interest and then sort of scaffold and supply information and materials so they can run with it. My son, for example, loves maths. Maths is his happy place. So we approach geography via maths, which was an idea I got from these books. He's happy because it's his beloved maths, and the geography is incidental. Another home edder suggested Risk today, as he adores board games. That will fire off interests which we can then follow, and I am chuffed to bits with the suggestion. The thing I do like a lot about unschooling is that it fires a love of learning, and that's important.
As I said, we don't unschool. He has formal lessons that follow the national curriculum, with a qualified teacher. But as I said before, I don't think anyone can claim only one method is right, and I know people who unschool to a high standard. Including teachers.
My approach to home ed is pick and mix. I use a lot of approaches. I think really, really good schools do the same, but they don't have the luxury of tailoring it to one child.
I do worry about the social side though. Having said that, plenty of kids in schools are isolated, bullied, and friendless, and aren't getting any sort of socialisation that does them favours. At least in home ed they would have friends, and wouldn't have their self esteem smashed to pieces.
The problem in discussion on home ed and school is firstly that it's usually framed as adversarial, with each posed as a terrible option by someone on the other side, and the evidence provided to support that is always the optimal or worst case scenario. I imagine most cases lie somewhere in the middle.
Personally, I think it's a real shame so few schools are open to flexi. It would seem to offer a really good compromise.