You can structure the system to cause an LLM an answer structured questions, Y/N or from a structured list of options, or with numeric weights against labels, and then use classical parsing to enforce a compliant response submission, and you do that for random batches of comments, then have another LLM summarise the survey response. It is quite possible to extract sentiment and key topics.

I don't think it's useful to throw your hands in the air and say LLM context statistics are ungovernable. Both context hardening and action shielding architectures are addressing this, and in combination with well designed pipelines the risk is controllable.