Basically Tielemans is Luiz replacement. We gave him a year to settle in and get used to our style and he was fantastic in the run in so grew into the role. Barkley is then relatively cheap backup for rotation and McGinn can also drop back into that area.
Tielemans and Onana as the duo for Belgium were excellent v England in March so that's probably some of the thinking, amazed Tedesco didn't start them in the pivot this summer.
That said I've generally been underwhelmed by Onana when watching Everton, never seems he impacts in their games like Gana does at DM and Doucoure can in the attacking role when Dycheball is clicking. Interesting what
@SilentWitness thinks on that as he wasn't even starting some of the crucial matches back end of last season.
He's had two years of regular prem football and still very young so we're banking on it all clicking in next 3 years I imagine.