Counter point: if a website was not designed & developed with federation in mind, it is very difficult to add it.

Intact, this is reflected by what the developers of Postmill (the software raddle is using and developing) say:

there are not, unless someone steps up to the table and meticulously plans how federation support would be implemented - allcatsarebeautiful (main dev AFAIK)

At the end of the day, many people just want a safe space and don’t care that much about the details. And the mods on raddle have opinions that sound safe to many users.