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You are not wrong: https://arstechnica.com/information-technology/2023/07/is-chatgpt-getting-worse-over-time-study-claims-yes-but-others-arent-sure/ and also https://duckduckgo.com/?q=chat+gpt+4+getting+worse

The more LLMs get exposed to data, the more they get exposed to wrong data. There’s also a vicious cycle problem that once LLMs spit out bad information, that bad information gets incorporated into LLMs new data sets, which makes them more wrong, so on and so forth.