The dynamic you describe tends to get stronger, when consultancies grow. The voices & competence of the technical people becomes less important when it comes to the business and efficiencies in utilization and the company brand start to matter more. The consultancy I worked at was not an incumbent, but an underdog competing with the big players, so the actual execution mattered more, when trying to win bigger customers. Even in consultancies, there are operational effiencies you get from having competent people. Mainly from having less middle management & account managers.
However, there things are useful for the consultancy's business only to a limited extend. You only need to be slightly better than the average consultancy and you're OK. So there is a point, when you either need to be great at sales or thought-leadering, or a consultancy can no longer increase your salary or provide your with work you find interesting.