Looking at the ages of the Avengers it's always so jarring to see the difference between Steve and everyone else.
Using the release date of The Avengers (April 25, 2012), I've made a list of Marvel characters' ages, youngest to oldest. (Not counting Peter Parker and Vision, who is like -2 years old. Wanda is 2 ages because her birth year was retconned in WandaVision).
Wanda Maximoff: either ±16 or ±22
Steve Rogers: ±26 years
Natasha Romanov: ±29 years
T'Challa: 31 years, 8 months
Sam Wilson: 33 years, 7 months
Stephen Strange: ±35 years
Pepper Potts: 40 years, 0 months
Clint Barton: 41 years, 3 months
Tony Stark: 41 years, 10 months
Bruce Banner: 42 years, 4 months
Scott Lang: ±43 years
James Rhodes: 43 years, 6 months
Phil Coulson: 47 years, 9 months
Nick Fury: 61 years, 9 months
See what I mean about it being "jarring"? All people in the room with Steve in The Avengers are older than him. Some of them even are older by literal decades.
I will never shut up about this because they literally put a 26 year old guy in a room filled with people older and more experienced than him, and then said "you're their leader now, figure it out".
And, looking at it from the other side, imagine Tony and Clint coming in and seeing that a guy who's FIFTEEN YEARS younger than them has to lead them into battle. And when Steve meets Sam, they share an age difference of six whole years.
I know 26 is a full adult, but considering everything Steve has been through in his life it's so shockingly young, and the way he was just thrust into the 21st century and made responsible for a team he knew nothing about is so sad.