I've worked at companies that don't touch agile, those who implement a kind of pseudo-agile, and those who invest in doing it properly. In terms of the accuracy of product delivery, there's a strong correlation between how well agile is implemented and how successfully projects are delivered.
I've worked as a Scrum Master across a number of squads, driving the process but ultimately trying to make the teams self-functioning. I was told by someone early on that the best thing I can do as a Scrum Master is try to make myself redundant - well I wasn't falling for that one. But there is truth in it. It's critical that team members are fully invested in the agile process, not standing passively on the sidelines. The best way to do that is to get them driving the ceremonies themselves (all of them, no heroes here) and be the servant-leader they need when they're blocked or looking for guidance.
Agile can be taken to extreme levels - scaled agile, SAFe, the Spotify Model. But it doesn't have to be operating at that level to deliver value. A team of any size will benefit from an honest agile process, working in thin vertical slices, delivering useable software quicker and having time to factor in technical stories as well as user stories, to keep on top of technical debt.