There's a setting you can turn on that increases the sensitivity, which should fix the issue. It works perfectly fine for me with a screen protector

I went from a Pixel 3 to a Pixel 7. I hold on to my phones as long as possible.

If you have issues with it detecting your finger try doing the "Check added Fingerprint" thing a bunch, apparently it can scan all of your finger more accurately, and get to the very edges and weird angles that the original scan never got. Seemed to improve the accuracy of mine a bit (never had big issues with it tho)