This is ridiculous. You have it 100% backwards. People tried these games because they were told they resembled Fallout and in some cases stopped playing them when they realized there were many important differences. Like, Underrail is a dungeon crawl for fuck’s sake. Age of Decadence has a lot less freedom than Fallout if you only plan to play the game once.
ATOM, on the other hand, is very similar to Fallout in terms of its setting, its themes, its character progression, its mechanics, and its mix of combat, exploration and dialogue. There are very few significant differences. If you liked Fallout, you will like ATOM. That’s simply not true of something like Underrail, which only appeals to a particular segment of combat/systemfag Fallout fans.