Armor is important but it isn't everything
Talking to a former Ranger down the hall, he just loves armor. Tanks and APCs make dandy targets.
Look, armor is important but it isn't the be-all and end-all of modern warfare. Given the vast set of anti-armor weapons out there (including those Russian wire-guided missiles that took out a couple M-1s this week), the future of heavy armor may be in doubt.
The modern Army and Marine Corps depend more on speed and flexibility than on heavy armored forces. Units like the 101st can hit, move, and hit again with a much smaller logistics train than a heavy armored unit and do it a lot faster.