Have McKinsey and its consulting rivals got too big?

In many cases, yes. But I wouldn't say it's not valuable if you're in these few verticals they care a lot about (one of them is mining, as an example). They won't provide you the data directly, but they do have it and it's central to everything they do - from across the industry, large and small clients, at all stages of life, and they stayed with many of them through significant transitions. They invested hundreds of millions of dollars into custom internal tools to make the data and derived analysis accessible to consultants. Where you have theories, experiments and anecdotes, they have statistics. And nobody has better than they do.

Don't fall into thinking they just want to make some easy money and don't care about your situation. They most probably saw hundreds or thousands of clients like you, and know that unless you're a unicorn, the "standardized" approach will be better for you - they synthetized it from thousands of engagements to be as simple and as idiot proof as possible. And here I mean idiots on both sides - consultants as well as the client. If you were an unicorn, you wouldn't need to hire McKinsey. Remember, most of us aren't Gates/Jobs/... This is just like tech startups thinking they're an unicorn and spending an absurd amount of effort (and thus money - also opportunity cost) on reinventing the wheel and building for infinite scalability, instead of simply doing what works well for everybody else.

Not saying they don't want money, but their approach to making easy bucks is to add a zero to their quotes, not by not doing anything worthwhile. The quotes seem crazy to us mere mortals, but the clients are usually happy - what's a few million dollars when they helped you save tens or hundreds of millions. You don't care how simple was what they did - you probably tried many times yourself before hiring them, and if they made a stupid thing work, you're grateful.

Sometimes it's really stupid - like a consultant randomly noticing that the client buys protective earplugs from 20 different suppliers while drinking coffee in the common area of 5th branch they're visiting; acting on it and making a much better deal (money and services-wise) with just one or two suppliers globally, and similar kinds of random ad hoc but monetarily significant optimization. That's where the templates come in - if you hire McKinsey they just ask "how do you do X?" - and if you say '"well we don't have a global process for that, each location handles it themselves", their reaction is to implement a template process - and I think that's good. Yes, the branches will scream bloody murder, but the corporate doesn't care - it's not their business to create cultural centers for adults. Create a lifestyle business for yourself if you want that.