Re: I can’t kick above the waist!
There’s nothing wrong with kicking below the waist. There are many martial arts that utilize the non-flashy low kicks. Probably the most effective is the oblique/stomp kick that targets the knee(below the knee), shin and the top of foot(instep).
When you combine with good hand combinations it is unbeatable and can be done in a non-telegraphic motion. For self-defense situation it is perfect to implement with other techniques. Here’s an example demo by Paul Vunak (I am not affiliated to their organization) https://www.youtube.com/watch?v=3DqJgrdzPHE
Hope that helps in seeing low kicks aren’t so bad.