bavard thanks for your question.
First and foremost let me be clear that Flagrow/Extiverse is a personal side project of mine. There's no affiliation to Flarum or the Flarum Foundation whatsoever. I am a team member and that brings in some confusion related to this project and my posts related to these sites. I am working on this by myself however.
Bazaar already offers an in-flarum method of searching through extensions. However installing and upgrading extensions remained to be difficult as Bazaar also uses composer behind the scenes. The successor website Extiverse offers a portal for easy extension discovery and a way for extension developers like @clarkwinkelmann to work towards sustainable, long term Flarum extension development by offering paid/premium extensions.
I do have some plans in mind to improve extension installation in the future, even simplifying the process for those on shared hosting environments with limited memory/disk space etc. But this has to wait for Extiverse to mature. Offering a replacement marketplace extension like Bazaar that would improve installation, upgrading and extension discovery inside Flarum itself is not likely to happen before that.
I hope this answers your question.