What a stupid video. That is like saying why cars don't drive faster than 30 years ago.

Of course cars ARE faster now, but that doesn't matter when speed limits haven't really changed.

Planes don't fly faster because it is not worth it. Pretty simple.

There is so much wrong with this video I don't even know where to start. First, there are only two types of aircraft engines, piston and turbine. When a turbine is used to drive a propeller, it's called a turbo prop. When he is talking about turbo props, he shows pictures of a piston driven propeller aircraft (Cessna 41x), and piston engines are the most common type of engine used on propeller driven aircraft, not turbo props.

He mostly gets it right about turbo jets, except again, every aircraft he shows when talking about turbo jets uses a turbo fan (the F-15 and F-16 both use afterburning turbofan engines). They get their thrust from the hot expansion of exhaust gasses, but he gets it wrong with turbo fans, which get most of their thrust from the bypass air from the fan.

Most airliners have wings designed to be used in low transsonic. They can't effectively go faster. They would literally lose lift if they went faster. Their wing shape is made to only delay the onset of shockwaves on top of the wing (flat-ish top), allowing it to safely creep closer to mach1 than otherwise, but not to operate within/past mach1.

Fan/propeller blades themselves are also mach limited.
(They can be designed to be supersonic, but then you end up with something like this... which in hindsight nobody wants : https://en.wikipedia.org/wiki/Republic_XF-84H)
A subsonic airfoil in a fan/propeller, operating near/at supersonic speed, loses the ability to move/redirect air, due to shockwave disruption of the airflow.

Fans/propellers with subsonic blades that spin at subsonic speeds are effectively speed limited. They lose efficiency above ~500 mph, where they begin to stop generating thrust as they travel faster. Their pitch has to increase higher and higher, until they are no longer much of an airscrew and more of a 'feathered' configuration.

Supersonic jet engines use intake devices (such as shock cones) to decelerate incoming air to subsonic speeds, so the compressor (itself a fan, i.e. a highly multi bladed propeller) can operate on that air to compress it and feed the engine combustion chambers.
Airliners have no intake devices to decelerate incoming air, and they would lose engine compression when entering near mach1 speeds.

Furthermore, their bypass fans (which are glorified propellers) would stop providing thrust.

You would need to design different planes (like the concorde). You can't just throttle up a modern airliner and go faster [than X limit] - like you can in a modern car.

-scheherazade