I’m trying to remove all page titles (including the blog title), and none of the edits I’ve tried have worked, including the default WordPress CSS method, or some of the other methods I’ve seen for your other themes.

Has documentation/development on Aqua stopped?

Thanks!

No, support hasn’t stopped, that’s if your support is extended!
REmoving titles, try this:

.page_heading h1 {
    display: none;
}