Material really makes little difference. It’s an issue of thermal mass and thermal inertia
Heat up a ballon fo 350° F, add a cake and the temp drops fo room temp range instantly. No thermal mass. Energy is a function of mass AND temperature.
Add some small clay pots of sand do your oven, and it will heat slower, but it will also maintain that temperature better. There is a reason why commercial ovens weigh hundreds to thousands of pounds. You need mass. It’s not optional
I have a pizza stone under the bottom heating element in my oven for exactly that reason.