I actually did just that. I (intentionally) joined the Army National Guard as an elderly infantryman. Better yet, I gave up my navy commission to do so! Why? To start with, the education benefits were spectacular. I got a Master's, two Graduate Certificates, and a Ph.D. without a penny in student loan debt while he Army paid my tuition. Next, it was fun. Weekends were like a hobby and as a senior NCO I got to do all the cool stuff but skip the typical officer admin stuff. Lastly, I have an over-developed sense of patriotism. I ended up doing two years in Iraq, two in Afghanistan, and one more in other GWOT locals. I got some great full-time trainer gigs, and even got to spend four months with a helicopter company as a door gunner!
Now that I am a grey-area retiree I have a lot of fantastic memories, will have a retirement almost equal to what I would have had from active duty, I have a chest full of medals and drawer full of photos. I have seen places I would have never seen, have a doctorate hanging on my wall...with my name on it...and a really fun civilian job that will offer me even more in retirement. When I die I can actually list all three services on my headstone!
So, yes, I did join the Marines without aviation, would have joined the Navy (in retrospect) without aviation, and did join the army without it.