Here's my take in regards to why more players is not actually sustainable.
I think the problem is that the pool of people who experienced old Roblox or old revivals has pretty much died out as they've moved on with life or onto new projects. They had a reason to stay, as they actually experienced old Roblox and enjoy the quirks of the older clients, even preferring to develop on old clients instead. They cherish the old and despise a lot of things that new Roblox stands for. The issue is that most of them have left in droves due to repeated "allegations" within the ORC or the fact that they're in their 20s now and their life situation has drastically changed. They've experienced all the drama that the ORC has to offer, and decided it's time to retire from this community.
The newer players are fodder. They are attracted to this because of novelty or some retro Roblox game like Forsaken and will move on far quicker when this novelty wears off. They don't have a true connection to old Roblox. They just like the aesthetic and will do something else with their time after their 3 days on here, when they realize that old Roblox games weren't inherently as interesting as modern Roblox games.
It's pretty tragic for Austiblox, as it exists in a post-golden era of pre-2015 revivals.