Poch isn't infallible. I'm simply saying he works with the players daily and is likely a better judge of form than you. He also has to make a decision on the value of a player who is still getting goals - goals being a commodity that, despite your bullshit, are the single most important thing an attacking player can contribute. It just so happens that right now Poch appears to agree with me and not you.
To put it simply, I'll take his word over yours any day because he is far more qualified. That doesn't mean I will agree with every single thing he says or does. But on this occasion the assessment of Dele is not as cut and dried as you are making it out to be and Poch has to decide that if he drops a source of goals he can replace those goals from the same position on the pitch. I think the only credible argument for dropping him would be if you could put a player in his position who could provide lots of assists for Kane, Llorente, Son, etc. Who is that player?