I installed the new GOG enviroment and found out that
I can't have easy access to any game's forum,
to GOG's forum,
and that I can't easily find a game's page to write a new review.

you can uninstall it anytime

It's not meant to be a web browser primarily....this is why I recommend people who use Galaxy also have a web browser for using the site to post stuff here.

I mean, yeah it's good feedback, mate. But it's not going to get heard just posting it in this thread in the General Discussion of the community forum. I'm pretty sure there is a specific place GOG wants genuine feedback to be posted.

Galaxy 2.0 beta does not yet have all of the features implemented which are present in the stable Galaxy 1.2.x release, however they are adding the missing features over time. This is all part of beta testing, so definitely stick with the 1.2.x release if there are features you require that are not yet implemented in 2.x.

All of the functionality you identified specifically above can all be done directly on the GOG website in a desktop web browser for the time being though until they've added them back to the client.

HTH