So...this is coming out of a purely intuitive (and probably wine-driven) state:
I am wondering if the ideal closet for you might actually be something like former forum member Clearly Claire's 10 item closet -- which changes every season.
10 items was obviously a bit of a misnomer. She did have a few staple items (jeans, some simple tops, sandals/shoes, a jacket, a trench, a classic dress) etc. that stayed the same and persisted in her closet across multiple years.
But twice a year, she'd go out and buy some new to her stuff (mostly at thrift/consignment) that would complement the core (mostly higher quality) items. And at end of season, most of those items would go "poof" back to thrift/ consignment for the next person to love.
She'd have a new uniform every season. With new-to-her (and sometimes classic, sometimes trendy) things.
And she didn't need to feel guilt about it, because she did keep her core items for a longer period, and she mostly bought the other ones second-hand.
I know Winnipeg probably isn't quite like Scottsdale for thrifting possibilities and not everyone enjoys/ has the patience for thrifting. But even if you purchased ten to fifteen or even twenty new items each season and gave yourself permission in advance to let them go at end of season, maybe you wouldn't feel such guilt about the churn. Especially if you knew those items were aiding a charity you support, going to a friend who loves your taste and can't really buy the stuff herself, going to a family member (there are lots of options). I think there is something in the giving yourself permission for a certain amount of churn that might, counter-intuitively, limit that churn over time, and also help you refine your style even further.
Because although you say you don't like trends -- your actions while you've been on the forum suggest that following the trends appeals to some part of yourself. You're divided about this (as many of us are!) One part of you wants variety, freshness, newness, change, visual stimulation. Another part of you wants peace, calm, a uniform, lower consumption, etc.
I don't have a solution to this dilemma, really -- maybe I'm describing my own psychology more than your own, so feel free to disregard. I just think, while we are on the "accept our aging bodies" bandwagon, maybe it would also make sense to accept our cravings for pretty new things and stop beating ourselves up about it. Maybe it would make sense to acknowledge that we contradict ourselves sometimes and that's okay because we're complex human beings. And yes, we can work towards a way of consuming that is better for the planet, but extreme solutions are rarely the best solutions.
In the "be true to yourself" line of thought — you already listed the items that you feel are core to your style persona. (You know yourself well!) So maybe you get those items in as high a quality as you can afford, whenever you can find afford them. Building this core capsule for your main seasons may take a couple of years, but patience will serve you. Eventually, you'll find items that have longevity for you. I suspect you already have about half the ones you'd want already!
(That was my strategy, by the way. A few years into YLF, I picked my key neutrals and started building my closet with my core items for each main season-- great blazer, simple dress, a suit, fabulous jeans, etc. Note: Five to nine years in, I am still wearing all those items except for the jeans which have obviously needed replacement. There's been churn of other stuff, but not those items.)
Then, you supplement those items seasonally with "the fun stuff" -- deciding ahead of time how much of it you'll permit yourself. Making a decision about numbers will help you become more choosy and deliberate.
Does that make any sense?