Struggled with sleeping bags for years before I even looked at pads. Honestly, my old bag was so lumpy it felt like sleeping on potatoes. Tbh, switching to a better bag made my cheap pad feel okay. One time I used a folded blanket under me and slept like a rock. Maybe it's all about the layers, not just one piece of gear. Ngl, I still dream about that blanket setup sometimes.
My old foam pad from 2015 still does the job for me. I tried one of those fancy inflatable ones and woke up with a stiff back every time. Maybe it's just how you sleep, not what you sleep on. I've found that a good pillow makes more difference than the pad. Sometimes the simple gear works better.
Read this article about how your body heat gets sucked into the cold ground if your pad isn't right... totally changed how I see it. They said even a great bag gets flattened under you, so the insulation there does nothing. That's why a cheap foam pad can work, it's all about stopping that heat loss. Makes sense why some people swear by a simple blanket or an old pad, it's more about the barrier than the cushion. Kinda blew my mind, honestly.