> how is this a plateau since gpt-4? this is significantly better

Significantly better at what? A benchmark? That isn't necessarily progress. Many report preferring gpt-4 to the newer o1 models with hidden text. Hidden text makes the model more reliable, but more reliable is bad if it is reliably wrong at something since then you can't ask it over and over to find what you want.

I don't feel it is significantly smarter, it is more like having the same dumb person spend more thinking than the model getting smarter.