I think it ranges from like 22-28% which is generally pretty good, but not the absolute top end. I do think most players cross (and often pass) into a predetermined area these days as well. For my money Andreas Pereira is probably the best around at doing that though and has been for a long time, but nobody is putting him in their world eleven.
Edit: Just had a look on
squawka - Tranmere and Andreas have serendipitously both played exactly 102 crosses in the league this season. TAA is at 26.47%, Pereira 32.35%. I've given a link but I suspect you'll have to input the player names and competitions yourself. I can't do anything about assist numbers without an amount of effort I'm unwilling to provide, but if you'd like to do it yourself, you could use sofascore to look up the assist types of goals players have assisted in order to get a general idea. Add up the number of assist types deemed to be crosses, divide that into their total number and go from there. As I said, effort.