Every time I try to level my Ender 3 v2 I get all the corners perfect when pulling paper in between. But for some reason, if all the corners are good the middle/center still has a bigger gap like 2-3 paper sheets. The prints do still look “OK” but I do have some sections where the lines won’t melt together.
A trick that helps a little is to put some kapton tape on the underside of the bed in areas that are too low - the glass has a little flex and it's possible to remove some warping that way, though 2-3 sheets of paper worth may be too much, plus you compromise heat transfer a bit.
If the tape isn't enough you can either get a new bed plate (either glass or upgrade to magnetic) or - IMO best option - get an ABL probe. It will compensate for the warping and make your life much easier.