... Well, the "gang of 4" (of which Deloitte is one) - from my experience - doesn't have the good expertise in-house either - when needed, they subcontract or outsource to the specialists... (And I am speaking as someone who has worked alongside them, and also subcontracted with them - I generally warn my clients about the A/B/Z-team game and that they would be better off by contracting with smaller agencies or individuals who actually would "embed" better in their project/team/initiatives)
And apparently so much so that they feel they can even use AI-created reports/materials...
I once saw one of Deloittes competitors build up a really basic Dynamics CRM, and then sent in some of their junior analysts to convince the customer, that they should just change their business practices to conform to the CRM as presented. They charged ~15 million for the service.
Deloitte really falls into the "We wined and dined and whored the decision maker" tranche.
And apparently so much so that they feel they can even use AI-created reports/materials...