Of all the departments in the org structure of Wikimedia, the Technology and Product departments are the two with the highest individual headcounts. Combined Tech+Product staff is slightly over half of the entire org's headcount. Most of the employees in these departments are technical in nature (either engineers of some kind or direct supporting roles), and you can make a fair case that they're all necessary operationally for the sites (maybe only Tech is necessary on a day-to-day level, but you wouldn't make it much further into the future without Product's work as well).

I would argue that the other departments/teams you listed are also necessary to the long-term health of the Foundation and the sites as well. However, even if we hypothetically decided that your whole list of "non-essential" org departments/teams/functions were a complete waste of resources (and again, they're not, IMHO!), those still don't comprise all the "other half" of the org's non-tech/product headcount, as you're still missing other essential teams like Legal, Talent&Culture (HR), etc, which are also significant chunks (Legal alone is a little over 10% of staff and extremely important and impactful!).

As to your point about budget growth: it was a different site and a different Internet in 2006. The org is growing up and becoming more responsible. It's getting more resilient in the face of an increasingly hostile Internet, it's getting better at fighting technical and legal censorship battles around the world, and it's slowly replacing the externalities of burning out a handful of highly skilled and overworked staff with more robust and "normal" staffing where employees can have real work-life balance and vacation plans or departures don't cause undue risks, etc. We're also trying to reach out to and support the growth of underserved Wikipedian communities around the world (both in technical and non-technical senses) in ways that we couldn't even dream of in 2006. Increased costs and overhead are to be expected with all of this!

Even at today's Tech headcounts, if you compare us to any other major sites of this importance, scope, or even traffic level on the Internet, we're still operating on relatively-shoestring tech staffing levels, especially considering we don't outsource core infrastructure to 3rd party services or clouds, mostly due to our strong user privacy and legal stances.