> unable to fully productize their solution
In my experience with this type of problem, it happens due to a failure of vision and leadership. The software company focuses a vast majority of resources on POCs and "consulting" revenue (really, rent-a-coder revenues) and these "consultants" end up failing as product innovators (i.e. they contribute practically nothing to the productization or even harnessing of institutional knowledge) and they also fail as true consultants (i.e. they do not have deep industry experience or management consulting prowess to be able to deliver unique value and engage with clients). Ultimately, this happens because leadership neglects product and becomes too caught up chasing deals and burdening the organization with custom development work to close the gap between the existing product versus market needs.
This is OK if your software company's consulting services are affordable. Enterprise clients tends to be quite accepting of the need for customization after product purchases. However they do not expect to pay McKinsey levels of fees (let alone $18M per year?!).
An alternative business model that seems to work is management consulting, where you can charge huge consulting fees (if you have earned the requisite reputation), and you can even cross-sell relatively low cost in-house software products or services alongside the consulting work. However, high value consulting engagement like McKinsey tend to last weeks (not years), making the expense palatable to clients (e.g. around 500k fee, for 2-3 consultants for a month or so). The difference between management consulting and enterprise software is that when paying $200k for 2-3 "millennial" "management consultants" for a week of work, the client doesn't expect delivery of a complete working software solution - the client only gets a PowerPoint presentation suggesting what and how management should do in order to achieve some given goals.
There is an interesting potential disruption occurring at the intersection of management consulting and software, but not much has changed yet with traditional business model divide between old-school management consulting and enterprise software, and Palantir doesn't seem to have cracked that code.