The tension of expertise and self-interest is a tough one (I live this every day). If you know enough to have a good opinion, you are probably either:
* a hobbyist fitting learning into the edges of the day
* an experienced person who is too busy to write up your opinions
* someone with a vested interest, selling something
That said, the post seems pretty innocuous on a close read: Datadog is expensive, observability is important, there are some OSS competitors trying to offer a complete suite, this is all similar to what happened in databases in the early 2000s.
Hard to argue with any of that.