So I am incredibly sleep deprived and have mad writers block, and with our boys birthday tomorrow (in ten minutes for me) I’ve done a little math.
So Bucky was born March 10, 1917. He fell from the train in January of 1945, meaning he was 27 when he “died”. He was frozen and only brought out for short periods of time for missions when he was The Soldier, (it’s pretty well agreed that they couldn’t keep him out long before becoming unstable) so he maybe aged a year, possibly two in the entire time he was with Hydra. So now we are at CATWS, 2014, Bucky is probably around age 28 biologically. He’s frozen again in Wakanda in 2016, so now he is around 30. Infinity war takes place in 2018, so he’s 32 before he gets dusted. 32. And besides that fact after his memories came back he probably still felt like that 27 who fell from the train (with a little extra baggage.)
So TL;DR, Bucky is still young, he’s barely lived in the years since being out of the ice. He’s still learning how to live his life, not just in this century but as a whole.