Is there an answer for athletics, music, robotics, and all the other after school teams? How does that work?

Of these, most are easily handled. I am in a midsized city and there are plenty of groups that offer music, robotics & engineering, speech & drama, etc. focused towards homeschooled students. That, plus the rise in homeschool "pods"/co-ops means socialization and activities are very available to students & parents who want them.

Sports might be the challenge. Many US states have athletic associations that handle most K-12 sports, and they require enrollment in an accredited member school. I am aware of several homeschool specific athletic associations in my area, but all are targeted towards religious homeschoolers. Not certain what secular alternatives would exist, but soccer is very popular & there are plenty of competitive academies that operate outside the school ecosystem.

My kids do Taekwondo and church youth groups. My eldest did not want to do robotics but he does run the Dungeons and Dragons group at our library. We do music as a family. My daughter does choir. My son has done drama but declined to participate this year. They have been homeschooled their entire lives. All three of them received something I did not, the ability to converse with adults from a young age. This is of course anecdotal so YMMV but I would love to see a study on the conversational skills of homeschooled students.

Homeschoolers form co-ops. A local one here does ballroom dance, tennis, basketball. There is often a youth symphony option in mid- to large-sized cities.

For STEM-type stuff, see if there's a nearby Civil Air Patrol squadron. That alone has tons of extracurricular stuff: search and rescue, help with earning a pilot license, robotics, drill and ceremony.

Homeschooling is not for everybody, but if you go down that route there's a lot of support.

To me, this question highlights the whole problem: This is not what schools are for.

Yes, it's great if they provide these things, but it's a distant secondary concern. I'd rather my kid get a great education and miss out on these things, than get a poor education but have access to all these.

But of course, as others have pointed out, it's a false dichotomy. You can have both.

Depending on where you live there are many options. In my school district home school kids can join any club or team offered by the public school system where you reside. Additionally there are numerous non-school related clubs and activities all over the place. My kids could play music with the local school district, with a musical education non-profit that is prolific in our area, or ( where they do play music ) with private lessons that have group classes, bands, and performance opportunities.

There are tons of clubs for such things. My kids are in a homeschool music program (and learning piano and, until recently, bagpipes); half of my kids are playing competitive sports via homeschool programs that compete with other high schools; one is getting his certification as a welder (as part of a State program that pays for it if one is still in high school). Because class times and locations are more flexible this opens up far more possibilities for extra curricular activities.

Often, yes. Where I live, home-schooled kids can participate in extracurriculars offered by the public schools.

i'm sure many others will reply as well but there's lots of extracurricular options for homeschoolers as well as social engagements. It's kind of like a shadow school system, there's associations and groups and other organizations built around home schooled children. My wife and I considered it but we have managed to navigate our public school situation well enough without me, or my wife, having to quit working.

Of that list my kids' top-rated K-8 public school only offers music. Everything else is done privately.

I went to public schools but still did that sort of thing through the YMCA and our church. At the middle school level and lower, most of those types of activities are community based rather than centered around the school, though that varies by area.