BuddyPress.org

You can still use the old “bp-themes” format (for now anyway) as long as you haven’t deleted the “bp-themes” directory.

I’ve quoted the following from:

https://codex.buddypress.org/how-to-guides/upgrading-a-buddypress-1-0-theme-for-buddypress-1-1/

Firstly you can revert to the old BuddyPress 1.0 theme system. Simply recover your /wp-content/bp-themes/ folder. This will revert BuddyPress into compatibility mode. You will not see all of the new features added in 1.1, but you will gain from performance and code improvements.

But be advised that, from what I’ve heard, the old 2-way theme format is going be phased out eventually in a future BP release.