for context on Langchain… it was started before the GPT3.5 / chatGPT API was released, so at the time it was better then using OpenAI directly for many use cases. There was also a bit of FUD around getting “locked in” to OpenAI and if you used Langchain you’d be able to easily switch to another model provider.
How it’s actually played out / my take: You’re probably better off just using OpenAI directly. GPT4 is better then any other model for most use cases and it’s easy enough to hit the API without adding the overhead of a lib. Use 3.5 if you need speed / a cheaper model. You also get Function Calling which can be really useful and I’m not sure how well langchain supports it.
If / when the open source models or Anthropic start to catch up, Langchain will be a nice abstraction option, but it’s currently not worth the overhead in my opinion.