What do all them players have in common? They're all playing in sides that are on the whole performing well this season and they've all managed to stay injury free for the most part meaning they're sharp.
Fernando has shown he is capable, it's coaxing it out of him regularly that's the issue. Don't think any of the 3 you mentioned are any better than him or would have fared better in our squad this season all things considered.
I'd say Kante and Dier have been rocks and linchpins for Leicester and Spurs respectively. Fernando hasn't. Granted he's been playing in a slow, inconsistant team. most of the games i see, he has been ineffective, slow, doesnt make a tackle, lets players run past him and jogs back when we are in trouble. I have to say that has to be someone better out there as a proper defensive midielder.