Enlisted is definitely not a "Stepping Stone" to becoming commissioned. Can you become commissioned if you are/were currently an enlisted member? Of course you can. Enlisted get selected to the academy or ROTC all the time. It's just not the simplest or easiest method to do it. Therefor, it's not really a stepping stone.
There's 2 ways to look at this. (There are others, but I will only count on the 2 that MATTER).
1. You want to serve your country in the military
2. You want to serve your country in the military "As a Commissioned Officer"
I am not dissing other people's motives for joining the military, enlisting, or seeking a commission. I'm simply not going to discuss other motives, because I believe that serving your country in the military is the most important reason. (By the way; there are other ways to serve your country other than in the military). But my point is; your pursuit towards the military, the academies, ROTC, enlisted, etc... all depends on which of the 2 above points of view you subscribe to.
If your main objective is to serve as a commissioned officer, then going the route of enlisted first; whether it's AD, Guard, or Reserve is a poor choice. It definitely isn't the natural order; or stepping stone; to reach that goal. As mentioned, it's actually a much more difficult means of reaching that goal. However; if your primary objective is to serve in the military, and officer/enlisted is 2nd or further down on the list, then there's nothing wrong with becoming enlisted if you weren't able to get an appointment to the academy or ROTC. You can serve; get educated; get your degree; and still apply for a commission later on if that's what you want. Unless things have changed, you only need 10 or more years as an officer (Out of 20 years) to retire as such. I know a lot of enlisted who got their degrees and were accepted to OCS with 6-10 years as enlisted.
Generally, these officer positions will not include most rated positions such as pilot or Nav. If you've been enlisted for 6-10 years, age will become a factor. Of course, if your main objective is to be a commissioned officer, you could take your chances as an enlisted. You could spend the first year in Basic Training and tech school. Then, getting your CDC's and 5-Level completed. Then, you can hope that you're still young enough to apply. Of course, you then have to get your commander, God, the Apostles, etc... to all support and agree to all that. Same with an ROTC slot. Of course, we're assuming that hormones haven't kicked in and you got married and started a family. That sort of changes a person's perspective on things.
As I mentioned previously; if you're main objective is to serve your country in the military as a commissioned officer, then you should apply to the academy and/or ROTC. If you don't get selected, go to college and join ROTC. (You can still join without a scholarship). Bust your butt and get offered a commission. If that all falls through, take your degree and apply to OCS. If you still fail to get commissioned, then you can consider going enlisted. You'll be 4 years older than most enlisted in basic training and your rank bracket, but it's still an option. Then you can apply for OCS from within once you've established a "military resume" and reputation whereby you have the support of your commanders. But going enlisted to officer at 17-18 years old, with the goal being to become a commissioned officer, is not the normal or recommended path. Best of luck. Mike...