I mostly agree with you but I wouldn’t go so far as to say the whole company has to adopt it. However you do certainly need the support from the wider company. I’ve seen scrum work really well despite waterfall being the predominant methodology in that business - there people were happy to embrace the preferred working styles of whichever team they had to liaise with. I’ve also worked in places where scrum failed badly despite the CEO pushing for it. Those places usually suffered from a blame culture that was also the CEOs doing and that blame culture meant that everyone was spending their time working against the best interest of any of the other teams. By “teams” I mean project managers, sales guys, support or operations teams (if they differ from your developers and/or DevOps), finance staff, directors/upper management and even your own paying clients (if you’re a hired service) etc.

I’ve noticed comments for and against scrum are often so focused on the technical aspects of the methodology that they overlook the human aspect. Which matters more in my opinion.