No, everything is NOT waiverable.
And with all waivers, it is the candidate’s responsibility to prove that it is in the service’s best interest to grant a waiver.
Seven years of active military recruiting and I never saw or heard of anything close to an age waiver.
FYI, as of a couple of years ago the Army was 50% short on Captains. The USAF and USN haven’t had much trouble filling slots (probably due to having fewer on the front lines) so they probably aren’t as flexible. But, the Army has been granting age and other waivers for quite some time.