It's not. The API is different, since GPT-4 is a chat based model, and davinci isn't. It's not a huge difference, but these little sort of things add up.
I've been using the JS version of langchain for a few months now, and despite there being a lot of valid criticism, (especially around the abstractions it provides) I'm still glad to be using it.
We get the benefits of a well used library, which means making certain changes is easy. For example, swapping our vector database was a one line change, as was swapping our cache provider. When OpenAI released GPT-4, we were able to change one parameter, and everything still just worked.
Sure, it's moving fast, and could use a lot better documentation. At this point, I've probably read the entire source code several times over. But when we start testing performance of different models, or decide that we need to add persistent replayability to chains of LLM calls, it should be pretty easy. These things matter to production applications.
Arguing that Tailwind is a leaky abstraction for CSS is like arguing that ORMs are leaky abstractions for SQL; hiding the underlying implementation isn't the point of these tools.
The biggest benefit is that you get a fairly well thought out API to work with. In the case of Tailwind, this a pretty flexible and good set of defaults that works for 95% of use cases. You can focus more on building classes for cases specific to your site, and not spend time rebuilding undifferentiated layout utilities.