I see what you're saying, but I suspect the top-down approach is not the cause of the usability issues with Anaconda. The problems are simply that it isn't always clear which buttons do what, which partitions are about to get zapped, and what the next action should be at any given point. It's not unusable, but it could be easier.
The Blivet GUI looks like it could fix many of these issues.
The Blivet GUI looks like it could fix many of these issues.