You often hear in conversations about structuing case interviews that you should not use standard business frameworks and concepts because they are too simple, and because every interviewer knows them anyway. It is most definitely true that you can't crack a realistic interview case by relying solely on standardized frameworks - but all those business frameworks and concepts are extremely helpful templates which you can put into your toolbox and use them (if not to the full extent, at least partly) when appropriate. Therefore such a standard business framework is just a tool - and the tool itself is rarely good or bad, it mainly depends on how and for which purpose you use it. I recently made a small survery among 120 of my coaching candidates, and roughly 9 out of 10 candidates say that their single largest issue in solving case interviews is getting the structure right. So this clearly is a huge pain point for case interview candidates, so it's definitely worth looking more closely at this matter. And in addition you might have heard the term "ABS" (Always Be Structured) - even though McKinsey is the most pickiest one when it comes to structure, all top tier consulting firms have a very strong focus on it. For our discussion, let's distinguish 2 parts of a typical case interview where frameworks might apply:
1) Beginning of the case interview
This is when you typically need to develop an overall structure on how you want to tackle this case. Interviewers often ask something like "What are the issues you need to consider here?" or "Let's assume you are the project manager of this consulting assignment - which areas would you like to investigate?". For this area of the case interview, I can at least agree to a certain extent with the existing answers to this topic. It is highly unlikely that you will be able for fit a realistic case interview question into a standard framework - if it would be that easy, nearly all candidates would make it into the top management consulting firms, and/or clients could solve their business problems without paying millions of dollars to consulting firms by simply applying a standardized framework. So, whatever your approach here will be, it needs to be very flexible because you will need to adapt it to a huge extent to your specific, individual interview question. And yes, it is your approach which needs to be flexible to make it fit to the case question, and not the other way round.
Approach #1: Get your hands on Victor Cheng's Case Interview Frameworks slides. In addition it is worth reading Victor Cheng's approach on case interview frameworks on his website.
Approach #2: Based on your case interview experience (i.e. having solved dozens of case interviews and having read through even much more of them) try to develop the first level of your case interview structure (or in other words, the main areas or buckets you want to investigate) 100% individually from scratch. Whatever approach you are using, this will mainly get you to the first level of your structure only. However, this first level will certainly be not enough to impress your interviewers - depending on the concrete case question, it is usually favored to have at least two levels of your structure, if not even three. And exactly for this second and third level of your structure, knowing the most common business frameworks and concepts is extremely helpful to all candidates. It is just so much easier to further structuring your main buckets from the first level if you don't have to start from scratch, but can apply existing frameworks and concepts. And even though you might just be able to use maybe 60% or 80% of a framework and need to adapt it to make it fit to the specific question, you are nevertheless already far ahead than if you would need to develop all that from scratch. Given the high mental pressure and time pressure in a consulting case interview, it is extremely difficult even for the best candidates to come up with the right issues, and at the same time remaining structured in a MECE way (mutually exclusive, collectively exhaustive) - this is just another reason highlighting the advantage of knowing the most important business frameworks and concepts, as they will not only help you to come up with a structure, but keeping it MECE and saving time at the same time.
2) Answering specific questions in later stages of the case interview
For answering specific questions sometime later in the interview, it is as important to remain structured in whatever you say as in the beginning of your case. Sometimes it might be well enough to use internal vs. external, short-term vs. long-term, pro vs. contra and similar basic structures, but more often than not this will not differentiate you from other candidates (don't forget - merely solving a case is usually not enough, you need to impress your interviewer by clearly standing out from the crowd of other applicants). Also here, knowing standardized business frameworks and concepts comes in very handy. As opposed to the overall case interview question at the beginning, most questions later in the interview are much more focused and narrow - therefore chances are higher that you can use a standardized business framework to a very large extent just as it is to answer the question.
I can just say from much more than 1,000+ case interview coachings over the last couple of years that a lot of otherwise very strong candidates would struggle answering this kind of more specific questions without knowing any standardized business frameworks - because it is still incredibly difficult to come up with a correct answer, and at the same time being MECE again in a tense interview situation! If you want to know what are the most important business frameworks and concepts which are relevant for consulting case interviews, have a look at one of my books focusing particularly on this topic: http://www.consulting-case-interviews.com/case-interview-frameworks. In addition to giving you a broad range of commonly used frameworks, I also put a strong focus on how to actually implement them step-by-step (you would be surprised how many candidates have at least a basic knowledge about the frameworks, but don't have a clue on how to actually implement them systematically in real life!). (And yes, I am 100% sure this approach works - there is a reason why some of my coaching candidates received their McKinsey offers directly after their first 3 case + PEI interviews, without even having to go through the final interview round)