This is your problem. Both should be too hot to touch and the same temperature. If the bottom hose is noticeably less hot than the top hose that means your heater core is leaking or has blockage.
Pull the hoses off of the core and flush it out with a hose. It might help if it’s simply blocked. If it’s leaking it’ll need replaced. I had a YJ with a tiny heater core leak but it was enough to prevent it from retaining heat. New heater core and I was sweating in 0° temps.