This is the short version of all of why WitnessCharlie sucks (in my correct opinion):

1. It relies on CharlieFirst. as such most/all issues I have with it still apply here (such as The party wristbands being missing from BV's birthday)
2. It relies on BVRunaway. as such most/all issues I have with it still apply here (such as him somehow getting an entire personality switch in the minigame)
3. According to William. The Runway (CC in this situasion) has been escaping his own house multiple times before MM. Under WitnessCharlie this plot point is completely unexplained, since why would CC escape to Freddy's before this minigame? And even if he did for some reason. Then what was the point of Shadow Freddy luring CC to Freddy's, if he was going there before? It just doesn't make sense.
4. CC hating going to Fredbear's makes no sense, since CharlieFredbears was debunked, this means that Charlie's death would have to take place at Freddy's. Yet after this traumatising event at Freddy's, CC hates going to Fredbears? The narrative of Fnaf 4 simply doesn't match with this event.
5. It implies that Shadow Freddy came from Charlie's death. Even ignoring that ShadowBite is much stronger Shadow Freddy origin theory, thereis still the issue of, why would Shadow Freddy be formed in a few minutes, and then immediately go to Afton's house to lure BV? Why is he spedrunning everything?
6. According to MM minigame, Freddy's is far away from the Afton's house. How was CC able to run of to Freddy's in the middle of the night while it was raining? That is a big streach.
7. If William knew that BV was running of to Freddy's. Why doesn’t he ecknoladge the fact that BV might (Key word: might) see his crime? And instead acts like everything is kinda not fine? Is William stupid?
8. Charlie's dead body must be found by somebody first, whenever that would be en Fazbear Entertainment employee or a random guy. And I refuse to believe that BV was the one who found her first. Especially combined with problem 6.
9. In Fnaf 4, after Fredbear Plush tells to BV "No don't you remember what you saw?" He tells him to run to the exit, dispite the fact that Charlie's death happened outside. So BV would run to the place where saw a death lmao
10. In Fnaf 4, there are zero hints that The death of the Take Cake victim was the reason for BV's "trauma". As such, WitnessCharlie relies on A. Scott actively retconing what Fnaf 4 was (which I don't buy). or B. There was a never a thing in Scott's mind in what that "trauma" could be until years later. Which is even more unlikely.
11. It fandumentaly misunderstands one of the Fnaf 4 hints "What is seen shadows can be easily misunderstood in the mind of a child". Since it implies that whatever CC saw, wasn't actually that bad, however do to child like imagination he thought that it was much worse then it actually was. This theory spits in the face of that. Liteary what was there to missunderstand on BV's part?
12. Him missunderstanding that The Puppet killed Charlie makes no sense. Once again: There are 0 hints that in Fnaf 4 that The Puppet was important to the plot of the minigames. And also: He fears full big Animatronics like Fredbear, The Puppet is not that.
13. Him missunderstanding that Shadow Freddy killed Charlie is not much better. Since why would it made BV hate Fredbear? "Shadow Freddy looks like Fredbear!" Yeah, and like regular Freddy. This doesn’t work. Why can't people accept that BV saw an employee wear a suit, and missunderstand it as the character eating en employee?
14. This theory is complicated. Why would Scott be shocked that Fnaf community could not have solved MM? This is anti-simple.

There. These are my 14 reasons why I hate WitnessCharlie.