Sorry for the late response. Thank you so much for your kind words about RetroActive. It made me smile to read your comments and I’m so glad it was/is your favorite. In particular I’m glad you like the color palette. I actually use this same palette in Systematic and expanded it just a bit to help make the systems and media pop even more.
As you said, you can use it as a custom theme since the files are available on the baxy-retroarch-themes repository. You can also simply replace all the PNG files within the FlatUX (or RetroActive) theme directory and that should make it work.
There were a lot of factors involved in the retirement. We received criticism about the size of the repository, so I relocated the source files for all my contributions and retired these two themes.
The RetroSystem theme is technically a fork of the original version of RetroActive, where the icons have parody logos on them. That original version is referred to as “RetroActive Marked” and is also still available over on the baxy-retroarch-themes repository, but is very incomplete at this point. Therefore, RetroSystem currently serves as a spiritual successor and it’s maintained by @alfrix and so I felt like it’s in good hands.
RetroActive was always intended to be a replacement for FlatUI, so it made sense to apply the extended color palette and remove the translucent borders. From my perspective, it’s the completed version of both RetroActive and FlatUI, and they both should be retired. But I don’t want to be the one to remove FlatUI from the repository, because I feel it should be a decision for the community to make.
Last but not least, it all comes down to the ability I have to contribute and maintain the themes. I would probably be a bit more motivated if the themes were available in Ozone, GLUI and RGUI. But since the themes are only a part of XMB, they tend to get buried and forgotten. No artist wants their work buried in obscurity, yet that’s effectively where we are, so long as Monochrome is the only available theme available in the other UXs.
At this point my primary contributory focus is on maintaining Systematic. From there, I’ll do my best to keep up with Automatic and FlatUX, along with contributing to Monochrome here and there when I can.