What constitutes being "old school" in the military?

US Marine Col (ret) Scott Ritter, uses this term "Old School" several times as he describes choices made in Ukraine: I summarize much of Scott Ritter's work here: https://tinyurl.com/tdwpt3kr

It's about attitude as much as time. You were raised a certain way before you joined, and that carries over. People like me believe in getting the work done quickly and efficiently so there is time for soldiers to conduct other personal military business. It return, the soldiers will work harder knowing they will have that time. That is me. Some schools believe that you keep the soldiers occupied with menial details until retreat.

Gawd, this comments made feel old...how about the PT test that included the run dodge and jump. the overhead ladder. the thrill of seeing a huey or Chinook close up (didn't ride in them just looked). humping a 90mm recoiless rifle and using a ta-1 hand cranked phone

Regarding the "If you ever" description: I never wore yellow nylon PT shorts, and I am not sure what a "gamma goat" is (unless it's getting 50CCs of Gamma Globulin rammed into each butt cheek in a 30ºF hangar at 0300 immediately after arriving in Korea, and then being put onto a "school" type military bus and bounced all over the Korean countryside for over an hour, with some guys bleeding through their uniform pants), but I've done ALL the rest at Forts Knox and Polk ("If God were going to give the World an enema, Fort Polk is where he'd stick the tube"!). We didn't have MREs yet, though - we had C-Rations. Particularly dehumanizing were the latrines in the WWII barracks at Fort Polk, with five toilets in a row in the middle of the floor - NO privacy whatsoever - I vowed to myself that I'd never take a crap in "public" again, and (so far) I haven't.

When I was still in, any reference to the "Brown Boot Army," as in spit-shined brown boots was "old school." Since then, it's become more about MOS identifiers. For example, I'm "old school," in that my MOS was 95B; today, it's 31B and the same for officers.
I joked with a Colonel friend of mind that they made enlisted the same as officer branch designators ... because officers would have a harder time changing to the enlisted ones. :)
Similar to the MOS designators, are uniforms. Old school wore PRESSED khakis or Dress Greens; but drove (mostly) hand-me-down sedans from TMP. Today, MP's wear what I call "pajamas," but drive actual patrol cars.
Old school would also be if you had C-Rations, especially if they still had smokes in them!

The uniform worn then has sure changed from today. Back then we thought old school was the brown shoe days.

When I was in back in the 60's what we considered old school was the brown shoe days. Old school now is the different uniforms from the past as well as weapons we qualified with.

Commissioned Officers were Commissioned Officers and NCO's were NCO's. Not "buddies," not "pals," not "friends," there's no reason for an NCO to be in the O'Club, etc. (Not saying that was better...but). Any Officer in the area, and EVERYBODY Snapped To! Until that officer said otherwise.

Being issued an M-14 rifle in boot camp, and at your permanent duty station. Going to radio school to find out that your "T.O." weapon is an "M-1911 A-1, .45 Cal, Semi-automatic, Gas-operated, Pistol. Then becoming an expert with both.

Depends on your age and when you served. My old school is OD Ike Jackets, brown shoes and boots but I'm 82. Women were in the WACS and only did admin and supply. Now, my daughter has 3 Air Medals, one for evacuating casualties under fire in N. Iraq on the Syrian Boarder.