The biggest problem facing Xavier on the offensive end right now is that they are shooting 32.5% from behind the arc, good for 224th in the country. Despite that gruesome number, they still take 38% of their shots from behind the arc, a number that places them just above average in the nation.
National averages can deceive a bit though, as there are 353 D1 teams but only 36 at-large bids. Xavier's 3P shooting of meaningfully below average on just above average rates seems worse in that context. Also, consider this: of the 75 high-major D1 teams only Penn State shoots threes more often but less successfully than Xavier. Penn State also happens to own a top 10 defense.
The problem ultimately comes back to the shot selection of Xavier's two highest-usage players, Quentin Goodin and Naji Marshall. Those two guys have a combined 22.7% 3P% while taking 42.5% of their shots from deep, an efficiency profile I'm confident would be dead last in the entire nation if you extrapolated over the whole team.
If you remove Marshall and Goodin from the equation, the remaining members of Xavier shoot 38.5% from deep and take 37.2% of their shots from beyond the arc. That would put them in the top 50 in 3P% and 217th in 3P rate. That is a disciplined, effective attack.
The cherry on top of this whole frustrating sundae is that Marshall and Goodin are both fairly effective from two-point range. Marshall in particular has been lethal when he puts the ball on the deck and crosses the arc, whether he makes it all the way to the rim or pulls up.
Right now, Xavier's offense is leaning into its weaknesses, and it certainly doesn't have a defense that can pick up the slack. Coach Steele has repeatedly said he has "the utmost confidence" in the jumpers of both Marshall and Goodin, but the numbers say the difference between this offense being solid and great is taking the green light away from the Musketeers two most profligate shooters.