Not really? The highest turnout for under 25s over the last 58 years was… in 2020 (~50%), when it was literally the same matchup . And that’s still significantly lower than other age groups (62% 25-44, 71% 45+).
There was a small bump in 2008 (assuming you mean Obama), up to 49%. But in 2004 when John Kerry was the candidate the turnout was about 47% so not like. A huge change. And nobody remembers John Kerry.
Looking across the pond, in 2019 when Corbyn was head of the labor party and ran on a lot of lovely progressive issues, the turnout under 24s (they use slightly different brackets) was… Just over 50%
It kinda seems like young people just don’t vote at very high rates, period. So it doesn’t make a ton of sense to focus on them over other groups if you actually want to get elected and hold power.
Also, more directly related to your original point, disbanding NATO and withdrawing support from Ukraine get us exactly 0% closer to either of those goals as well. They just show that Stein is an unserious politician with extremely specific opinions on NATO and Ukraine for reasons I’m sure are unrelated to her funding.