> Is it possible to get constructive feedback? sure, maybe.

Not maybe, definitely.

> it possible to get a specific teacher's feedback? Not really.

Yes actually it definitely is.

> Is it possible to guarantee it will be productive feedback? No, especially if the student has to/gets to interact with it.

Yes it is possible to guarantee it will be productive, and far more consistently productive than what teachers can achieve.

There are going to be educational contexts where LLMs can't provide productive feedback (because LLMs aren't relevant to the learning objectives). There are also many contexts where they are exceptional at producing productive feedback. Especially in grade school and qualitative undergrad courses.

I am pretty sure what's happening here is you are conflating LLMs with ChatGPT and other chat interfaces. That's a bit like conflating an internal combustion engine with a tractor, and then basing your experience with tractors on an opinion that busses can't exist. Indicated by this thing you said: "No, especially if the student has to/gets to interact with it.". It seems like you haven't considered that LLMs can have any kind of guard rails or custom instructions applied to them, can be packaged or constrained in how the user interacts with them.

An interface can allow a student to submit a draft, get static personalized pedagogically-optimized feedback tailored to the teachers criteria, learning objectives and reference material, without any way for the student to get any other output.

I find it both funny and a little irritating how confident you are that this isn't possible, because I've seen it with my own eyes used in both graduate and undergrad contexts to great success.

In a way you have answered my original query, which I am grateful for: "Why aren't all educators tripping over themselves to use LLMs to maximize access to timely constructive feedback?"

You're indicating the answer is because most educators are confidently incorrect about LLM capabilities. Plausible I guess.