The Fuso is something of an acquired taste. It indeed has low range, even for a bb2, and the gun setup can be annoying for what is best used as a hit-and-run ship. That can be a difficult hurdle, especially if IJN is your first bb nation. However, even with at-level gunners, it still hits like a sledgehammer, so your only obstacle is getting within range. Once there, and especially if you have BB3 level gunners or higher, you are king. Even with 14s, you have more firepower than some bb4s (*cough*H39*cough*), and can frequently 2-shot bb5s.
It thus simply becomes a question of getting there. Conserve overheat, look for blind and/or distracted bbs, and go in for the kill when you see a chance. With its high firepower and slim profile, a properly piloted Fuso is extremely difficult for most opponents to handle once it gets in range.
Another thing to note is that it has more useable displacement than the Nagato, while the same number of crew slots. And frankly, if played right, you'll level faster in the Fuso. Since it hits harder and the bonus for doing damage against higher level BBs more than makes up for the above-level penalty, I actually stuck with it all the way to Yamato.