I was with you on the “spark joy” eye roll...until I tried it. There are so many items that are just “meh,” some that are “ugh,” and some that are “ooh I love you!”
I’ll give you an example. Functional, solid color T-shirt’s are my best example of “meh”...so many because it’s essentially my “uniform” (that I use as base for my scarves, because I’m not creative enough to use other types of tops..but that’s another discussion) I picked each of them up: most were “eh..it’s ok” and then there was the one T-shirt that was an “ooh aah”... perfect fit, great linen fabric, and made me feel good when iI wore it. That was the “aha” moment. Why not keep those and get rid of the “not quite right ones”. It seems so obvious now. I got rid of 75% of my clothes. I still have some “ooh aah” items for my imaginary lifestyle..honestly those should go but they “spark joy” so ...
Anyway if you’re going to consider a wardrobe downsizing, try picking each one up and see what emotion comes up. There’s bound to be one.