Welcome to the community!
Here’s a good resource for a lot of commonly-needed things: https://modxcookbook.com/
And here’s a link to a recent post where Rob Carey shared a project he worked on: My Best MODX Project Yet. Connected Image Library
There are a lot of advantages to working with MODX but, in my opinion, the biggest is developer experience. MODX is simply a joy to work with. A possible disadvantage might be the lack of pre-built, plug-n-play themes which would allow one to quickly spin up a generic site, à la Wordpress or Squarespace. But I don’t think generic sites are really what MODX is for. Rather, MODX is all about customization and creative freedom.
$0.02
I’ll leave you with this old but still-fitting meme:
