I guess a case can be made either way. It might depend on the preferences and particulars to the family.
For example, I know for me I would make a terrible home school teacher, and my kids would've missed out on so much. For other families, home schooling is a life saving, terrific idea that works for them. My brother sends his kids to what I secretly call a "hippy-dippy" school. No letter-grades, instead teachers give a strength-based narrative conversation....not my thing. Yet my brother's family love it, and when his kids and their classmates transition to the public high school they keep pace and exceed the other kids in test scores and overall academic functioning. Both these models of education aren't for everyone, but it doesn't mean kids can't thrive.
There are plenty of families at my kids' school who opt out of the Japanese track for whatever reason, likely including the reasons others have mentioned in this thread. I can imagine that an immersion program forced into existance because non-English speakers can't adapt any other way or an immersion program shoved down the throats of public school families would be a disaster. In our situation, I don't get the sense that teachers are trying to get away with something. Rather, it takes a huge commitment to success because no extra money is allotted to support the program, like a bigger budget for teachers from Japan. It's fundraising, lots of parent and teacher volunteering, and consistent success by graduates over the almost 20 years of its existance. If language immersion was a smoke-and-mirror to divert attention away from a subpar education, it would be evident by now, hopefully.