efbgen, I feel your pain! I have the same problem with... most of my clothes! These heatwaves are real style killers. Rest assured, your purchase was wise and useful. Only not so useful this year so far. This is happening to me with items bought last year and the year before, that had sat in my closet because summer weather is so freakish. This year, they came out to play almost exclusvely!
When I was in Calgary, I was reminded of the subtle but crucial difference between the West and East coasts in term of chill. Even in a heatwave, Alberta air will sometimes brush your skin and give you goosebumps, making you want to reach for the next topper in hand, even as you're walking down a sunny street. One minute later, you're sweating profusely.
I had an epiphany when I realized it's all in the wind. Out West, in summer, you're fine as long as you have a wind breaker. Even the thinnest ones will do. In the east, the humidity makes a windbreaker uncomfortably sticky.
So keep your blazers, as they will fine their vocation.
Another way is to look at them as the center around which you build outfits, instead of considering them as add-ons. I find the perfect add-ons a rare and precious occurence anyway. However, if you start with the topper, and put the rest on as an afterthought (an important afterthought, I will give you that!), you can get workable, stylish surprises. For example, put the navy blazer on: then grab some jeans or silk track pants to put underneath and a white tee or cami. Get footwear to match blazer, not top. Or get unapologetic casual footwear that almost look like an excuse because you had to have something in your feet, but the main character, the star of your show is the blazer. Pay attention to collar line with blazer on. Compliment the blazer with jewelry, not tee shirt/blouse alone.
Take the white one, then find some skirt or dress to pop out of. Not the blazer covering an existing outfit. White blazers look good with printed tees, especially rocker ones. Or with very sweet, romatic basics such as a flowy, full skirt or fluid wide leg pants.