Each weapon actually plays really well into variety and a flow in the combat.
Rebellion is in the middle, offering both, great ground combos, aerial combos and drop attacks. Osiris is on that lighter end, offering a distinct ground game, but many more aerial combos at the cost of keeping you in the air (even going higher), with no ways to bring people down. Arbiter has little aerial game, but gives more options for drop attacks, and has some great moves on the ground if you want to commit to them.
To the point, the Style system works on variety, right? So they wanted to give each weapon a purpose, but then also urge you to cover that weapon's shortcomings with the other weapon's strengths. There's a distinct flow you can get into when using the weapons, and it's done in such a way to encourage you to do so.
E&I, sure they're not "as powerful as they were in DMC3" and whatever, but NT wanted to make sure people didn't try to blaze through the game with just guns - they wanted you to really play with melee combat system they had in place. Firearms in this are used much more for resetting, cancels, and adding variety to combos. They can also be upgraded, of course.