It sure feels like everything after GPT-4 has just been an incremental improvement (putting aside multimodal capabilities and longer context windows) - GPT-4 Turbo, GPT-4o, o1.

GPT-3.5 with the ChatGPT front end was just such a massive improvement over everything that came before it, then 4 months later they release GPT-4 which was a significant improvement but more importantly gave the impression that progress was actually accelerating, then for the last 20 months we got incremental tweaks and new models that are a little better at certain tasks and a little worse at others.