I have experience not being promoted. I retired in 2018 as a twice passed over O-3E. I made O-4 after I retired (board was not on time and convened too late to matter lol) got the certificate and everything. Nobody but your peers care about how good of stick you are (sts). It's unfortunate, but that's the way it was when I was in. I wrote awards for my airmen, I helped write OTS packages for a few (one even became an 11H) but refused to write any for myself. I loved flying and my brothers and sisters (there were some bad ass female 11Hs) I flew with. I had some awesome Sq/CCs and DOs as an 11H as well. But if you’re not in the plan, it doesn't matter. I had a clean record (No trouble), I just chose to stay at the squadron level instead of taking the jobs that get you promoted. Prior to my promotion boards, I was a flt CC in a big squadron, I was the CCV/Chief for a few years in another one while balancing the budget for that sqd as well. I didn't care if it looked bad on my record, it was what I needed to do to help my CC at the time, he was my brother. If your peers were in charge of promoting people, the good sticks would have an edge but that's not how it worked when I was in. The board doesn't care if you can fly the shit our of your MWS, they are looking for the "clues" from leadership that you're part of the plan.
Edit 2: Nothing against my 11H CCs and DOs all solid (for the most part lol). They told me it was a bad idea to just fly. I just liked it too much.. lol and beer and ladies lol.