Does the Army constantly change the pattern of organizational clothing when it changes personal clothing?

Considering I am wearing my 2nd version of Dress Uniform (I refuse to purchase the AGSU), and my 4th pattern for field uniform (BDU, DCU, ACU, OCP).

That depends on how you define "constantly".

The U.S. Army Center of Military History has some great reference material for a variety of topics and one I came across a few years ago is a "Survey of U.S. Army Uniforms, Weapons and Accoutrements" by David Cole*.

If you REALLY want to get into the nitnoid of how, where, why, then delve into the darkness called "PEO Soldier" and look at the portfolio of the Product Manager for Soldier Clothing & Individual Equipment*. There actually is a rhyme and reason behind the uniform decisions and it isn't just some senior officer or NCO that needs a bullet on their evaluation.
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* https://history.army.mil/html/museums/uniforms/survey_uwa.pdf
* PdM SCIE - https://www.peosoldier.army.mil/Equipment/Equipment-Portfolio/Project-Manager-Soldier-Survivability-Portfolio/

WTF I wore the od wool pants/shirt for every artic like exercise for 23 yrs.

It may all boil down to money. Money that some contractor gets for developing something that they can talk "Big Army" into buying.
The BDU was a good uniform and lasted my entire career. The OG-107 ("Vietnam" Jungle Fatigues), which were the same design as the BDU and the DCU but in the Rip Stop Cotton-Poplin in OD Green, was issued to us in the 1980s at Fort BRAGG (B R A G G) for field use. The OG-107 was awesome. I was issued the BDUs, could wear the OG 106 as an optional uniform (OD Green that the shirt tucked in), was issued OG 107s and DCUs, and endured a year and a half of the ACUs.
The OG-107 was by far the best. It dried quickly when you were wet, starched to a razor edge for formations, parades, and inspections, and was not the national debt of Bolivia to replace them.
I applaud the adoption of the AGSU (Pinks and Greens) for doing what every survey that the Army Times conducted the entire time I was in the Army about changing the dress uniform. Every year, Army Times surveyed the Army to see what changes they wanted to make in the dress uniform, and bringing back the World War Two uniform was always on the top. Now, if they would bring back the Khaki Uniform that was used up until 1985, I would be happy as a tick on a slow Beagle.
My son is in the National Guard now and was issued the AGSU and the OCP uniform, both of which are good. I really like the field shirt/Combat shirt concept. Prevention of heat injury while wearing body armor is a great thing.
I hope the Army will STOP listening to the Good Idea Faries and stay with this uniform bag for a while. This stuff is too expensive for the troops to keep changing, because we all know that Good Idea Faries are a very, very bad thing.