>>723099598
>RA gets multiple new sets every week, and a lot of those require a lot of technical skill
A little misleading. The actual process of creating sets typically requires no technical skill. This is part of the reason why RA succeeded. The barrier to creating most sets is low, which increases the number of set developers.

>It is simply impossible to create a reasonable alternative without steal RA's existing content
Personally, I think cloning RA would be a small-minded aspiration.
It'd be better to have an open achievement ecosystem, intrinsically unreliant on a central authority. The focus would be on portability and locality of achievement sets, which would be standalone self-contained packages like a zip file containing things like the achievement logic, icons, and metadata.
You'd have a translation layer connected with Retroarch or whatever that can identify these standalone sets, capable of importing them into a local database. Sets are typically only a few KiB each even uncompressed, so space wouldn't be an issue. If you wanted, you would also be able to connect to a server hosting their own achievement sets. Each server could have its own rules and leaderboard, so you wouldn't be completely dependent on one central entity. Progress on a server could be duplicated onto your own device, so if you leave a platform, you wouldn't lose any achievement history or progress.

That's my dream for achievements.