Seat tube too. I have a fixed fork mountain bike with 67/74.5° head tube vs seat tube angles and a gravel bike with the classic 71/73° or what used to be classic on XC bikes. The gravel bike climbs really well with a higher gear but I wouldn't tank over bumpy terrain with it, the mountain bike is really stable on descents and on flats, climbs okay. Of course a MTB with 63/78° like the new Marin El Roy probably doesn't climb that well?

You should try some of the newer bike geometries. It's amazing what they can get away with.

I'd take a modern slack head tube geometry over an older bike for climbing any day. I've owned plenty of bikes through the years and I'm not going back.