I have been nodding along with a lot of the comments here Debbie - casual has become such the new normal that it does feel almost strange to dress up - even a little in some areas or environments! That said, I have never wanted to fall into the trap of looking like I didn't care, esp. as I get older. Over the years here on YLF I've learned that the basic things like the fit, material thickness, drape, color palette, silhouette, shoes and of course good grooming can make even the most casual outfit appear more "dressed" in a good way.
I feel like I *can* wear a simple v-neck tee with jeans and feel put together as long as the fit is right, nothing is wrinkled, torn or stained, etc. I might cuff up the jeans if needed to avoid a "too long" look, add a belt and semi-tuck the tee, wear a simple pendant necklace, clean shoes (sneakers work fine if they are clean and work with the color of the outfit) and of course pay attention to hair and other grooming.