I'm not sure what you expect him to say?
It's not that I'm surprised he didn't say more. I just wanted to correct the impression that he'd apologized, because I think that's inaccurate. They should apologize, but I don't know that a speech to Congress is necessarily the right place for it.
Japan owes apologies to China and Korea before the U.S. IMO. My wife is Korean and the Korean people still harbor resentment towards Japan for their WW II atrocities to this day. My wife is in her late 40's so she has memories and stories passed down from her parents of what they went though during WW II.
China, Korea, Guam (which is a US territory with a painful memory of Japanese occupation), the Philippines, Vietnam, Laos, Cambodia, Malaysia, Singapore, Hong Kong, Australia, and the US. Even Taiwan, if you go back a bit.
I have visited Japan. The Japanese people are aware of what Japan did during World War II. For young Japanese people, though, they really have no connection to WW II Japan. What exactly does a Japanese person born in 1992 have to apologize for? Similarly, I don't expect a 22 year old German to have to apologize for what the Nazi's did.
Individually, nothing. This is about the nation as a whole.