This is definitely subjective. Having only played Lexi's route so far, there does seem to be less moments when the MC could interact with Lexi than shown (like he pretty much ignores everyone then and the limited Lexi interactions could be really improved, her showing she is more connected to him for example, which are comments Holly was given instead for some reason), and if the non-CeCe routes are similar it's easy to see where some might feel that CeCe is the only viable story option.
Something to keep in ming however, which is pivotal to the story
CeCe's role is exactly as needed, she is there to help everyone else, when she is also a wreck. As the MC notes, she's probably one of the strongest ones in the group, but incredibly fragile at the same time. it balances out for sure. I don't know if she is "best girl" since all of the women are very different and have different life experiences and strengths/weaknesses. CeCe might be "best girl" if someone has a 'protective' nature and they as the player want to rescue her as occurs in the story.
I agree this is probably one of the top 5 VN's I have played, and anyone who doesn't react to Chapter 5 lacks something emotionally I believe. That chapter, even though I knew what was going to happen, still hit like a truck. I just wish some of the montage scenes could be paused because they had some great moments in them that have to be watched multiple times.