Your question points to the difference between possession and identification. You have a car, you aren’t your car. Similarly, you have a brain, but you are not your brain or the happenings within.
Nobody said nonduality is easy. Through meditation you can separate mind from awareness, then awareness from identity. As you keep diving deeper into the workings of your mind and how you experience them, you’ll eventually have an experience that your aware mind, having been turned off, couldn’t process or make a record of. You’ll have to reconstruct this experience later by taking stock of your mind and what changed.
No matter what the Buddhists say, true dispelling of the observer or normal cognition is not something you want happening all the time, nor is that happening all the time something that necessarily characterizes nonduality. Nonduality involves lack of identification with awareness, not actually changing the things you are aware of. Not the actual changing of the functioning of the mind.
I like to use the pain meditation to illustrate this. Let’s say I slap you lightly on the wrist. It hurts a little but it’s not anything that affects you a whole lot. This is pain without suffering. People can even learn to enjoy the feeling of pain, did you know that the chemical that makes hot peppers hot is actually a poison? We’re just too big for it to have that effect. Instead we come to enjoy the feeling of heat. Capsaicin will actually make you really really sick if you ingest enough of it. But in small doses it’s tolerable, enjoyable even.
You do not identify with the heat of the poison you just ate, so you don’t perceive of it as distressing. You can disidentify with all pain this way, in fact the Buddhists made a religion of it. There is a practice of self-mummification that you should really look up on Wikipedia.
When you disidentify with pain, it’s like playing a magic trick on your mind. You feel the pain sensations, but you don’t perceive them as pain. If your mindfulness is good enough, you can make any pain “go away” this way. The episode that sticks out to me as a kid is when I broke my arm once, the process of setting the broken arm completely broke through my mindfulness, and it hurt like hell. The actual breaking of the arm did not do this.