No, that's just the business tagline. Consultancies purity spiral on Goodhart's law. They're worse than useless, and it's their "cult"-like behavior that is the basis of their entire business.
You HAVE to believe they bring in value because... well, you gotta believe.
Management consultants are useful in a few ways: 1) you get a dedicated team that works full time on some issue and 2) you get people who have seen how a lot of other companies have done things.
> 2) you get people who have seen how a lot of other companies have done things.
And the result of this at companies I've worked at that had management consultants change process was to just bolt on some processes with adaptations to the business, selling it as "BigCorp™ does it this way and you should too" which eventually backfired when these reorgs and processes don't pan out because they were made for the needs of BigCorp™, not the business they are consulting in.
There is loads of cargo culting from management consultancies.
You HAVE to believe they bring in value because... well, you gotta believe.