While I had the same experience as you in high school (and primary school language learning was altogether a farce), I found the experience very different in classes at university. I think the primary factor was that there were a negligible number of unmotivated students.

Listening to other people at my level didn't seem a particular detriment because teachers have to speak at roughly my level anyway. They made more mistakes, but the instructors corrected them, and the corrections were valuable since they were often the sorts of mistake I'd make myself. Textbooks are trite, but since their main competition in the internet age is materials put together by dedicated but ultimately pedagogically-unskilled amateurs, I think they're better than most alternative prepackaged materials.

What I will acknowledge is that private study through a flashcard deck is probably the best way to acquire vocab, but that was never my biggest challenge. My vocab has consistently been on the large end of other people I've learned with, just because memorisation suits my personality (and I suspect that's true of a lot of people here). That never, though, translated to being the best in class - ability to fluidly construct a sentence beats out perfect word choice every time. It's also very easy to pair with a taught class, since there's no downside to learning extra vocab on the side.

Classes move a bit slowly, but I think the rationale is valid: You're here for three years anyway, you're probably trying to get to around B2, so we'll train you up to B2 in three years.

I'm not going to argue that it's as good as a private tutor, but it was closer to second-best than worst in my experience.

I moved to Norway as an adult and took classes meant for adult learners. And honestly, there were things I might not have grasped otherwise. Of course, I was in class 15-18 hours a week, was surrounded by Norwegian to a point (English is used a lot: Norwenglish is a thing). I had speaking practice in a nursing home two days a week for some months. Our teacher was a native speaker.

It is honestly helpful to have other learners to practice with: They, in general, have the same knowledge base as you do. Workbooks give repetition, and is helpful with things like grammar and word placement. (I only used a workbook with the first 2 books in the first year). The textbooks had common-sense dialogs and things: These focused on everyday situations (small talk, apartments, speaking about one's background, basic job stuff, and so on). A lot of reading introduced these things or made sure to include information about culture or civics.

And honestly, if one only went to school, participated, and did the homework when we had it, one would learn some language. You were simply better off if you worked on it yourself. I'd certainly not have as much understanding of dialects or grammar trying to learn Norwegian on my own.

This was completely different than the classes most folks had back in the US, generally in high school. I got more instruction as an adult in a day than we usually would get in a week back in high school. I had native speakers teaching. The class was taught in the target language from the first day.

Not all class is the same, and some are very beneficial.

> I'm convinced that a classroom is the worst possible environment for actually learning a 2nd language.

Surely classrooms are the worst environment for learning anything. Of course it's going to be easier to learn any subject if you have a dedicated teacher who makes sure that you understand the material before moving on and keeps you engages. However is it worse than anything? Classrooms usually end up giving you access to a teacher who you can ask questions to and receive a comprehensible response.

Just like in any subject if you actually don't take the effort to study from your own curriculum you're going to be relatively behind. If all someone does is attend their CS lectures and do the bare minimum on their homework assignments then they're effectively wasting their time as they'll be behind their peers who met with professors to collaborate on research projects or with peers to found a startup (in addition to side projects).

Classrooms for any subject are a bad environment because like you stated everyone else has a chance of participating. In addition the material is suited for the majority and isn't personalized. When I was learning about geometric functions in middle school no teacher ever related it to cosine similarity that can be used in NLP.

However 1-on-1 lessons are expensive, so aren't classroms a good enough compromise?

It's the gulf of the difference.

Most other subjects, I'd say classes are a bit sub-optimal, but still a great choice if you aren't working with unlimited resources. There's value in hands-on group projects, labs, instructor feedback, etc. And, in most subjects, there are plenty of successful people who did a lot of their learning in a classroom environment.

Language learning, though, I'd say that a classroom is worse than nothing at all, if you're motivated. And not just a little worse, like, a lot worse. In language learning, it seems remarkably consistent that the vast majority of people who achieve much success eschew classrooms entirely.

That's one thing I disagree with in the original post. Like you, I created my own Anki deck and I'm convinced it's a better way to learn.