Dele is one of three things
- He peaked at 21, add to the 5 million other next great british talents in the PL who peaked and never pushed on, will stay in PL and do the occasional highlight reel brick for the next ten years that will remind everyone of what could have been
- He's a luxury player that only works when setup a certain way that the team needs to carry (i.e. floating runner off Kane with Eriksen supplying)
- He just isn't working hard enough in a system (they why could be happiness/motivation/whatever), with a manager that expects everyone to put a shift, no passengers
My opinion, it's a mixture of all
- He hasn't kicked on as a player and in the EPL the opposition typically adapts very quickly to counter in a season or two (why Kane is amazing)
- He always was a luxury, at his peak he would be very ineffective for long periods of a game, then pop up with a goal/assist
- His head isn't in it, or he hasn't figured out what it takes to get him back to that space
So what we have is two players (Dele & Bale) on different ends of their careers who by talent should start every game, but by output don't deserve to displace anyone in front of them.