I think the CB options look fine with both Yoro and de Ligt. Yoro will hopefully develop and and get better because the potential is there. And de Ligt isn't a easy player to out-duel in space because for one he isn't slow and he knows how to use his strength to out muscle a quick opponent. I think one more CB should be bought and maybe that CB should be left footed. A player who is strong in defensive duels, especially across the ground and has the ability to carry a threat in possession by way of passing vertically and carrying the ball forward.
The big issue imo is the midfield and having a strong base in midfield with the pace, power and technical ability is the key to having a fluid system of play. It doesn't matter what formation it is, the main thing is to have high caliber players in the team to play a more expansive brand of football. And with the way many teams are playing a expansive game in the present day, it's absolutely imperative to have CBs and deeper midfielders who have the ability to win duels in a higher line when the high press gets bypassed and also have the ability in-possession to get the ball forward at a good level whilst retaining a good level of ball retention. If you as a team cannot do the aforementioned tasks within the areas mentioned above, then the system of play will not function and it will severely limit the teams capabilities. And that's the problem with our team and it needs addressing quickly, and if that happens I can see a quick turnaround where a system of play would be visible for all to see and we'd then be on the road to creating a well oiled machine that would have the potential to send us on a upward trajectory.
Right now the team is over reliant on the backline to progress the ball with Bruno also being utilised deeper in midfield to progress the ball forward. The issue here is that the backline end up going direct due to inefficient support in midfield and Bruno dropping deeper doesn't solve the problem either because as good as he is with passing the ball long he doesn't have the ability to evade the press, or have the physicality to halt transitions in larger spaces against the counter.