That "sound underwater" thing is the perfect way to put it. It feels like we're constantly sold these half-fixes that promise a simple solution to a noisy world. You buy the gadget or download the app expecting peace, but it just adds another layer of hassle. It's not just headphones, it's everything from sleep aids to productivity tools. They all seem to miss the basic point while still taking your money.
Three times I've bought expensive noise-canceling headphones thinking they'd fix my focus. Markm27 is totally right, they just add another layer of stuff to mess with. The first pair I forgot to charge, the second pair's app kept crashing, and the third pair made my ears sweat so bad I looked like I went swimming. I'm starting to think the real problem is my brain just doesn't want to focus, not the leaf blower outside or the coffee shop music. So now I just sit there with regular earbuds and pretend I'm in a quiet world, which is basically the same thing but cheaper. Half-fixes are my specialty, apparently.