Why there is no CF in FC Mobile ??

Because there was a lot of complaints about too many cards being CF and it only featuring in a couple of formations, so based on player feedback, EA removed it.

It’s the same for LW/LWB and RB/RWB now being the same position 

Wait, what? There are still CF cards in the game, and so are the positions in the formations. If you place a CF card OOP, then you significantly lose OVR also, if you put a non CF card into CF position (either CAM or ST) you also get a significant OVR loss.

Or do you mean there won't be any future CF cards and the last decent CF was 101 Puskas?

dzrtr ah - yep - CF is still there, RF and LF gone, along with LWB and RWB - thanks for correcting that :)