A major difference is they weren't being sold as "assistants" back then. Now they're a product expected to act a certain way. While some LLMisms probably come from shared poison in the pretraining corpus, many of them also come about as a result of trying to make them more appealing as a product. Most open weight models are just a company's product, post-instruct and everything. Base models are a different ballgame (and are becoming increasingly sparse), so effectively no matter what you're pulling in someone's model that's been trained into the chirpy "executive assistant" personality we all hate. Some models are worse for it than others.

You can tell the post-training makes all the difference though. Gemini has a different stink to it than DeepSeek.