Who said he's not responsible for it? He's accountable for everything that happens with this team. My issue with the armchair analysis on this is that people try to claim some issue with X's and O's that are based on a dumb and generally untrue narrative about tactical inflexibility that popped up when Underwood was at OSU or just some personal preference to have basketball look like it did 20 years ago, or 40 years ago, or whatever. People (and at least one player) screamed bloody murder about the five out sets they ran earlier this year, and he changed it, and the team still has the same issues people were pointing to. Maybe it's not the X's and O's?
As for last year, he had an All-American post player and a bunch of guys who could shoot, and virtually nobody who could attack the rim, so what did you think the team was going to do? Trent did his best but he was too small to do it consistently. Plummer was even smaller than that. Da'Monte shot 28% -- 28%! -- from inside the arc. If you think you're going to be successful running the Princeton offense to get back-door cuts for a bunch of clean-cut young men against the defensive schemes teams run today, you do you, I guess.
Underwood has had some pretty successful offensive teams over the years. The question that remains is whether this is an issue related to his current personnel, or if it's a trend. He's responsible either way but I don't think this year's offense is just what you get when you get Brad Underwood.