7/4 ratio should be simple, but it'll sound out of tune (over 30 cents) in a normal context. Many BP intervals are just as simple and they'll sound very out of tune to people unused to them.
That said, we're trying to isolate things that are typically not isolated. If you get to 7/4 by following the harmonic series, it will sound in-tune. If you get to 16/9 by playing and applying 4/3 twice, then that will sound in tune. Unsurprisingly the second option is more common in music.