I've never been able to find what I needed quickly in the old UI, always felt disorganized and random. I like the one on the iPad a lot better, I find it way easier to navigate, so I'm happy for the change.
Over the years, more options were added to the system settings, and the old UI did not lend itself well to holding all those various options/configurations. It became a burden to find exactly what you were needing; not to mention it was beginning to look "out of place" with the rest of the OS.
So yes, it functioned poorly, while also looking terrible by today's standards.
I've never been able to find what I needed quickly in the old UI, always felt disorganized and random. I like the one on the iPad a lot better, I find it way easier to navigate, so I'm happy for the change.