Personal opinion: it doesn't seem to have gotten as much love or attention as many other commercial projects, currently being under Apache Foundation and just slowly trudging ahead. Someone else mentioned it being more popular in China which is fair, but also means that the docs and blog posts about it etc. aren't getting as much attention in the west and other places.
Personally, for many of my use cases (typically simpler projects, <20 services per environment), it's good enough, the platform support is mostly there for most of the popular languages: https://skywalking.apache.org/docs/
The docs are also there and configuring it is actually easier than Sentry, because of fewer moving parts: https://skywalking.apache.org/docs/main/next/en/setup/backen...
I don't particularly like using ElasticSearch which seems like the "happy path" but ES just loves to eat memory in general. Thankfully, there are actually some nice options for alternatives here, I wonder why other projects haven't embraced such modularity: https://skywalking.apache.org/docs/main/next/en/setup/backen...