Oooh! You had me at "navel gazing"!!
I am nodding along with your entire post (I feel like I could have written it myself!), and with Janet, Lisa, and Joy. For me, comfort is most certainly two-fold of emotional and physical.
I think you are right that it's largely lifestyle-driven. 10-15 years ago I, too, lived in high heels, crisp button ups, fitted/tailored blazers, and I spent most of my time in a corporate setting. I went from corporate to home office, professional to tech work, urban to suburban living, California to Chicago climate, so everything regarding how I dress has to (still) be re-evaluated. Now, I am chasing kids, caring for and renovating our home, and working from home part-time which all seem to require different clothes!
I think you are spot-on with aging being a part of it. I find that I have become increasingly intolerant of feeling constricted (great word, Lisa!), and of being too hot or cold. I can't function if I am too cold or too hot, so layering and fabric composition is key. Layers can't be itchy or stifling, I can't feel sweaty or clingy, and I have to look neat enough to run out to meet my coworker in a moment's notice. Like you, I also feel out of sorts if I am not dressed similarly to others in the room. So, if I go to a PTO board meeting in a velvet plum blazer and pointy suede boots while everyone is in black leggings and trainers, it makes me want to crawl in a hole and hide!
I am still attracted to structured pieces (blazers, pointed toe shoes, button-up shirts), but I try to find them in a more relaxed version - like, I will go for a washed chambray shirt instead of a cotton poplin, or a plaid chamois instead of a solid sateen.
Like Joy, there are those things I feel extremely comfortable in that I wouldn't be seen out of the house wearing (which triggered my loungewear capsule post!). Yes, I LOVE my fuzzy fleece Snoopy pants, but wouldn't be caught dead in them at the market!
I suspect there is a lot of overlap between us, so I hope you will keep me posted on your direction and findings. I love the addition of "ease" to your descriptors and think you are on to something!