Hi Queenie - welcome! I am also in my 40s with two teenage girls. I know what you mean about the quality seeming to get worse and worse.
Since I work from home, I actually do my errands and such wearing smart casual clothes. Part of it is that it just feels so good to have a reason to get dressed up and out of the house! Also it ensures I get full use out of my better clothes. And I am sure it helps that I happen to live in a town where everyone seems to dress up all the time. You rarely see gear in the grocery stores here, and if you do, it's LuLu Lemon yoga gear, nothing sloppy.
At first I felt weird about dressing up but what I found helped is to cultivate an attitude of "I'm just running by the grocery store on my way home from the office."
I am petite so I rely on Ann Taylor, Ann Taylor Loft, and Banana Republic for probably about 90% of my wardrobe. You may also like Jcrew as well. Quality at AT, BR and Jcrew is pretty good; ATL is hit or miss.