was there ever a setting for this? I always used gSwitch or gfxCardStatus to varying degrees of success

It was labeled "Automatic graphics switching" in past releases. It appears to be gone completely. I just confirmed it was under Battery on 12.5.1. This is a shame. The Intel GPU on the 2019 MBP is pretty anemic and it is definitely felt when programming in some editors.

You can still do it, but it’s not exposed in the UI anymore.

I don't think it was ever officially in the UI beyond "allowing" certain applications to use the dedicated GPU inside a MacBook Pro. The only reason Apple even added that was as a battery conservation concern.