I joined when I was 20. I'm out now with my car paid off, a decent job that I learned in the military, no debt, an A1 credit score, travelled the world, fukked a lot of hoes (jk, but if you get stationed overseas you can add this to your bio lol), free school, VA loan, free health insurance for life, I'm about to hustle the gov't out of a disability check...for life, and also a lot of intangible benefits lol.
I would say joining at an older age could have been better. A lot of the things that you have to adjust to are just listening to people. With age comes that maturity and most of the older people were mostly pretty chill and just did what needed to be done. I think it's a good gig. I was AF. If you go do IT. HANDS DOWN. I know people that got out of the military, came back to work the next day on some call me Tyrone now shyt

, and are puling in 6 figures. No joke. Use the military for all you can because they'll for sure use you. If you have some more questions ask me. I'm all for people going to the military, even if you don't stay in. It allowed me to build an excellent foundation for myself, and I never saw a war zone.
I never planned on staying for more than one enlistment so I can't speak on the retirement and making rank and what not. I think your age is perfect for going. I'm at the point now where people around me are starting to have kids, get married, or make great strides in their careers. I am not able to do that because I'm still in school and kind of figuring out things. I guess I'm just not on the timeline I wanted to be in my head...