You're leaving out one pretty crucial variable here which is the different positions in the back 3.Conte started Bastoni in 1 game out of 7 this season. Make that 1 out of 9 as Bastoni won't play v Barca or juve. Doesn't make Bastoni a bad player, just a young and inexperienced one and Conte used him for rotation purposes as we have a horrible schedule. I actually praised Bastoni in the match thread a couple of times..
Ranocchia is dead last choice for LCB and I will be amazed if he starts there even once this season. I doubt Godin will play there either. D'Ambro will eventually but of course hasn't yet. Bastoni is thus either 2nd or 3rd choice LCB.
LCB and CB are not the same position.
BTW here are Conte's thoughts on Bastoni:
Finally, Conte spoke of 20-year-old defender Alessandro Bastoni who made his debut for the Nerazzurri tonight.
“Half of the Serie A wanted him and I was against letting him go. I want to work with him, I’ve seen his potential not only physically, but also mentally. He does what you ask him to do right away. Alessandro will certainly be useful in the future, but he’s also useful right now.”
“He’s an important option to have and again I repeat, I’m taking risks, last match with Biraghi, and today with Bastoni. But I have faith in them, I have no problem putting them out on the pitch. Their team-mates also have faith in them. We continue like we have so far, with humility and a great desire.”