It is very hot on the mountain in summer and it is barren with no shade or trees. I remember seeing people climbing up with no water wearing flip flops on their feet, no sunscreen or hats.
I was just talking to a friend who has never been to Yellowstone. After your recommendation I suggested she visit the Lassen volcanic area if she can’t make it to Jellystone (she drives back and forth to CA like you do). I will as well. I have been fortunate as a non-affluent person to have visited Yellowstone and the geothermal area in New Zealand (Rotarua - North Island) and also Iceland (near Reykjavík but pretty much all of Iceland is a geothermal park). And I saw a steam vents on Mt. Baker near Bellingham and maybe Mt. Rainier as a kid (memory is hazy on Rainier, maybe not).