The size of this motor is moderately interesting, but the power density doesn't really matter for most of the things you just mentioned. Almost every one of them is limited by the amount of batteries you can put in for both weight and power output reasons.
What do you mean? Modern LFP cells have quite high power density. LTO is even higher.
An e-bike with a 100Wh battery and a 300W motor would be extremely useful if it were light enough: you could carry it up stairs, onto trains, etc easily, and it would give plenty of boost to navigate traffic for short distances and make it easier to go up hills. The idea would be that most of the energy would come from the rider. 100Wh of modern LFP cells doesn't weight very much, but you still need to carry around the motor and the structure to support the motor.
In an airplane, you need a lot of power to take off, and weight is a big deal.