BCG dinged me after the final round for "not displaying enough enthusiasm". I have my first interview with McK in 1 week...

Were you hungry to solve the case ? I think thats what they meant by "not enthusiastic enough" Perhaps you asked all the questions any standard candidate would ask - but not beyond it to fully nail the case. Introversion is somehow in my opinion irrelevant to your case interview performance. Actually it could be an advantage.

If you are introvert, there's a good chance what you think would consist of being a "sycophantic little fuck" is just the baseline for others. Also, being energetic and enthusiastic =/= being a groveling suck up. You should be genuinely excited and enthusiastic to be there (it's freaking McKinsey...) so show that and you'll be fine. If you don't know how to do that, you're probably trying to get into the wrong industry.

I've had to give this feedback before. As others have said, it's likely how you presented yourself during the case. They wouldn't expect you to come in waving pompoms and chanting "BCG! BCG!"

It seems like you might be presenting yourself too passively during the case study and may not have been confident with what you were saying. You obviously gave good answers but they didn't understand whether you really want to be there or cared about what you were doing. The firms want someone who is lively and engaged. They want someone who will go in and sell their clients that they are doing the right thing by spending big bucks to have that person there. Drink three cups of coffee, wear a bright colored tie, get blown by a hottie the night before... do whatever you need to do to be a bit more amped up in the interview. You can still be in introvert, you just have to try a bit harder to show a "spark" if you are.

Regarding the "insights" bit: the best thing you can do is run cases with someone who is seasoned in their career. It doesn't matter if they are in consulting or work the line in manufacturing - just having something to tie those insights to will be beneficial. If that isn't an option, study current events in the business world. Look at large deals, hot companies, and failures circling the drain. You have the answers - you just need something to make them feel special.

You have the right "meat" in your responses, this is all feedback about "presentation". Good luck, you can do this!

Two things. 1) You said "reach feasible solutions but lacked business insight when synthesising and elaborating the final recommendations" This means you didn't do as well on the case as you think. Maybe you got the math right. Maybe you laid out a nice structure. But you were unable to translate this in a meaningful way to what your client should do and what that means for their business.

2) "Sycophantic little fuck", however negatively you put it, is actually a part of this job. At the very core, much of what consultants do is to generate ideas, then convince oftentimes less talented and more egotistical people to embrace and implement those ideas while giving those individuals the feeling that they own and will get credit for that success. Deferential? Subservient? Yep. And guess what? if you can't convince a client that you're happy to be serving them, invested in their success, and willing to run through walls to get them there, you're going to be short-lived. Enthusiasm in the interview is just a sniff.

Did you say 'that's a very interesting problem!' convincingly at the start of the case?

I've had this before. Seemed like a bullshit reason imo. I'm guessing there was something else or perhaps nothing else and they just liked another candidate more because of their gut feeling, etc.

Be more enthusiastic

Feels bad dude