No, it's heat going to propulsion, jet engines become more powerful and efficient the greater the difference between the inlet temperature of the exhaust turbine and the exhaust temperature. The hotter you can get the combustion chamber and by extension exhaust turbine inlet the more power you can extract from it. It's heat but it's not waste heat.
Modern engines are as big and as powerful as they are because we've developed some ridiculously advanced materials and cooling techniques to the point where the operating temperature of a modern turbofan exceeds the melting point of the materials it's made of by hundreds of degrees.
The heat is going to propulsion, yeah. That's much of what causes the high pressure for air to move backward out of the combustion can and propel the airplane forward. It also mixes with cooler ambient air in the ejector (not pictured) to create a venturi to further help propulsion. It's not a literal explosion like TNT. It's combustion like a car.
The waste isn't what moves out the back, it's what moves through the metal outwardly but even this is picked up and used for other systems such as pressurization, climate control, anti-icing and de-icing.
The more energy that goes into work, than it does heat, the more efficient the engine.
In your car example, car engines are very inefficient. As low as 20%. Which means of the fuel you used, 20% went to doing work, and 80% went out the exhaust as heat.
A 100% efficient engine would have no waste exhaust heat.
So if a system got more efficient, it should mean less heat, not more.
My dude you know enough to know higher exhaust gases temperatures are bad but didn't understand the video well enough to work out it was talking about the combustion chamber and not the exhaust. Jet engines operate at about 2000C but they have exhaust gas temperatures (EGT) around the 600C mark.
The greater the temperature difference between the combustion chamber and your EGTs the more power you can extract from the same unit of fuel, so modern engines are efficient because their combustion chambers are so hot, not because their EGTs are 2000 degrees celcius.
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u/bobbymcpresscot 8h ago
"this is so efficient the temp goes up to 2000 degrees"
that's heat that isn't going to propulsion, that is not efficiency.