Everyone agrees, of course you can get in without Victor Cheng's material.
He is very good at getting to the essence of the case, but at the cost of over simplifying a little bit at times. Still, do not overlook the fact that probably >50% of all MBB admist over the last 5-7 years have used his material (I did too fwiw), so his methodology and recommendations are effectively part of the standard now: you have generations of MBB interviewers who will expect you to be generally consistent with his teachings. To do well, you therefore need to AT LEAST do what he suggests, but also go beyond so you create positive separation between you and the other candidates.
Here is another way to think about it: assume a sales job comes with a very rich compensation structure, making it highly coveted. Any good sales person with a high school education should be able to do well, but the job posting requires a BBA + MBA preferred. Victor Cheng's method is the BBA level. Can you get the job without? Probably. You would improve your chances with an MBA however, which here would be "Victor Cheng + additional prep".
Hope this helps.