I do/have used a Kruve an I've been very surprised with by my findings with it. In my experience, even very nice grinders I've tried still produce like 4% fines, and some midrange ones are maybe only 6%. By percent, that's significant enough, but in the end it's less than a gram difference, and therefore sorta hard to use as the comparison between 2 grinders. Sifting is also essentially worthless for that purpose if you didn't take the same measurement when the grinder was new, since you have nothing to compare the present to.

I honestly think your best bet is going by taste. If you feel the quality of your cup has declined, that's probably the best way to be sure. Everything else is just a proxy for trying to determine how the cup will taste.

You can use a methodology from soil testing for this that doesn't require extra gear. Sieves (like with soil texturing) will give you a faster more accurate answer. Here it is:

Get a narrow glass jar. Fill it a little way with ground coffee. Fill with water. Shake. Set on shelf and wait a few hours up to a day.

The larger pieces will settle first and the finer settle last. You can see the sorting of them through the glass. If you use consistent amounts of coffee and the same container, you can measure depth of layers. I.e. this grinder makes .5cm of fines to 3cm of ideal to .2cm of too large.

Bonus is you can use this method for making cold brew, so you don't waste the coffee or water.

Forget the Kruve. You need this:

https://www.amazon.com/Retsch-60-159-000999-Standard-Vibratory-Diameter/dp/B00C1NM660

Some folks do but it that is just a bridge too far for me.