A cotton shirt suits anyone who wants something that looks like effort without actually asking much of you in the morning. It's a good fit if you like a bit of structure, a collar that holds its shape, something you can throw over jeans or tuck into a skirt without thinking too hard. It's less good if you hate ironing and won't admit it, because the cheaper weaves crease the second you sit down, and if you're after softness against the skin, this isn't that, cotton has a crispness to it that some people find bracing rather than cosy.
This is a spring and fairly reliable autumn piece for me, less so in the depths of winter unless it's doing a layering job under a jumper, and genuinely useful in high summer because even a thicker cotton breathes better than most synthetic blends when the weather turns sticky. I've worn the same pale blue one to a work thing with tailored trousers, then slung it over a swimsuit a few weekends later with the sleeves rolled, and it did both jobs without complaint. It sits well with a plain pair of jeans, obviously, but I think it earns more interest with a pencil skirt or wide leg trousers, something with a bit of movement to balance the shirt's stiffness. Knitwear works over the top in cooler months, a fine merino or a cardigan, because cotton on cotton can feel a bit flat. In the shop, check the weight before anything else, poplin is light and can go slightly see through in bright light, oxford cloth is heavier and more forgiving, and a cheap, thin cotton will show every bra seam and every crease by lunchtime. Look at the buttons too, cheap plastic ones crack oddly and the thread around them is usually the first thing to go. Check the collar is interfaced properly rather than just folded fabric, you'll feel the difference within a few wears.
What changes with age, and I mean the shirt's age, not mine, is that good cotton softens in a way that actually improves it. The first few washes it's a bit stiff, almost unfriendly, and then somewhere around the tenth wash it starts to feel like it's yours, the collar relaxes, the fabric loses that showroom crispness and gets a slight give to it. Cheap cotton goes the other way, it bobbles, the colour greys out in the wash, and the seams start to pull. A decent one gets better looking scruffier, which is not something I can say for most things in my wardrobe.