Delurked, I know exactly how you feel. And no - you aren't being picky at all.
But it is true that not everything you try on in the dressing room will tell you it's "issues" immediately. For example - a pair of jeans that bags out...a cami that rides up, or a top that starts to fall off the shoulder during the day. All these "issues" are only revealed with wear, which is where the challenge lies.
Let me tell you, you're not alone. This happens to ALL of us. My trying extra-hard to gauge quality & fit & durability of an item at time of purchase doesn't automatically mean it's gonna be comfy for all day wear. But....I do have a strategy.
1) You were wearing an outfit where ALL 3 pieces ended up being uncomfortable. Unless you can afford to just get rid of all such mediocre clothes right away & shop for new items, I recommend you try pairing something "fussy" with something "guaranteed to be comfy". For example - wear those jeans with a very nice & comfy shirt that's a workhorse. Add a belt. Wear that top with a very comfy pair of jeans that work well for you, and with a tank instead of cami that doesn't ride up. Or try a cami with lacy straps underneath and wear at home to lounge in. I find cute tops that fall off the shoulder (unintentionally) rather alluring. Point being- if only 1 item in your outfit feels "fussy", sometimes that's not a deal breaker. But if at the end of the day you still hate the item of clothing despite pairing it with your comfy favs, donate it ASAP.
2) Keep a mental note of all these items that are so-so. If you come across a replacement, buy it and then put the original problem child in the donate bag.
3) Also make a mental note of what brands/cuts/styles you prefer. Stick to these when you go shopping to eliminate mediocre items. Also keep a mental note of what to look for in terms of comfort from your experience with these 'mediocres'.
For example, I know from experience that I do best with mid-rise or high-rise jeans. No matter how well a pair of low-rise jeans fit me and how comfy they feel in the dressing room, I don't buy them anymore. I know I will find 'issues' with them later. Same for cap sleeves on top that have a higher neckline....they make the top bunch up unattractively over my bust as I move around when the sleeve pulls the whole top up. No matter how cute a top, I don't buy such sleeve anymore. And i have the same problem as you with camis. They ride up and I find that very annoying. My solution is to avoid camis all together. 99% of my summer wardrobe doesn't need one underneath. For the remaining 1%, I have started wearing a tank underneath. And I buy one size big....that makes it not ride up, somehow.