Players need to keep performing to earn their place. Dembele isnt playing well and the goals are doing little to mask that from the coach and the supporters
Rafinha isn't performing though, he looks completely out of place. Was bad against Real Madrid, wasn't benched. Was atrocious against Rayo, we'll see what happens in the CL midweek. Wouldn't be surprised he starts again. Valverde actually thinking that Rafinha out of all the players he has at his disposal is the one to deputise for Messi while he's on the sidelines is IMO a pretty damning indictment on his decision making.
If you want the team to be picked on merit and performance, an honest approach is a must. There were extended periods during last season where Rakitic was heavily underperforming, yet he started week in week out. Suarez also. It is very clear that there are players who have preferential treatment for whatever reason.