banana, I don't think it's a reaction to that all, and I hope you don't actually think that. To me it sounds much more like a reaction to the stressful times, when we're restless or emotional turmoil dominates our every thought it's bad enough dealing with that day to day, it's not a part of us we're actively willing to share with the rest of the world as overtly. By dressing more nondescript and 'calm' you're simply presenting the opposite, either in hopes of getting there, grabbing hold of it prematurely (a positive attitude, I feel, you're looking forward) and/or simply because amidst all the chaos it's something you can control. Not looking a mess makes you feel like less of one, it's quite a common coping mechanism, especially when an illness is involved.
There was a good documentary on this a few years back, by a French/Dutch woman and she too was exploring the subject of why this appealed to women so much in this time/age group/etc. She explored it a little broader, global influences, a rejection of the male gaze, amongst others. It's called It's in the Sky. I can only find an online version without subtitles and it's mostly Dutch with a bit of English and French. DVD for sale here but it's less than half an hour.
Interesting we're talking style, I'm reading through Lidewij Edelkoort's trend forecast for 2018 (the only one I bother with) and it's a lot about these subjects, I'll recap later.
I personally park 'signature style' with the capsule wardrobes, etc. and think much like Flo on it. It feels too much in opposition of both fashion and time to arbitrarily declare yourself done at some point. I switch things up all the time in reaction to the tides, there are certain constants, which other people might narrow down as personal style. I've always been very aesthetically geared, things of beauty fascinate (though not so much people, those I find dull), expressions of craft where human touch is legible, small defining details, little things that reveal the hand of the designer, materiality and flow, etc. It makes my tastes expensive, and I don't mind paying for that as it actually feels like my money is going towards something but it took a few years to get over the snobbish aspect of it in what is a very horizontal society and equally for my age to catch up with as well. Then again there are things I've loved since childhood, it drove my mother mad because I insisted on wearing white dresses all the time, the most impractical thing ever considering I ate with my entire body 
. Still love them, I don't really bother with a LBD but a LWD is a mainstay for me, which is quite comical since I've always been very anti-marriage. Equally a version of a beige trench has always existed in my wardrobe. So I think it's possibly a combination of things, signature pieces, an attitude to grooming (I have always been low maintenance, and always will be, it's mostly down to being fortunate that I don't need much doing to), and understanding what appeals to you, the things I've worn to death and still mourn were usually not the things you expected them to be when first buying them and the reverse, very practical purchases can get very stale.
Those in the heat, just how hot and humid is it or do you have staff because my main issue with those temperatures is that shirt dresses and similar all sound ideal I could not stand to iron a thing in those temperatures, even with the idea of aircon, may be down to me though I'm not a good one for heat. Aside from that, it all starts wrinkling, etc. far quicker (especially in humidity), which is why I think the very practical stuff is so popular. I mean we are talking temps over 25C minimum, right?