Well this is only my opinion which is totally subjective
- Mods obviously (even on consoles)
- The fact that in Fallout the story takes up less space. There are rarely quests where there is only storytelling. It's always some dialogues, an area to explore (loot / fight) and a some dialogues. So even completely ignoring the story, you can more easily "have fun". Unlike Cyberpunk where there are often quests where it is only narration (Both sides, Blistering Love, The Information,...)
- The "inifnite" quests and loots/fights. I could spend hours just redoing quests/exploring for loot (even just junk items to build my awesome base), money or experience because it respawns every time.
So unless you're really addicted to history and the Cyberpunk world, it's less obvious to dive back into it and have as much fun as the first time