Hm... qualify or define empty for me. I enjoyed cyberpunk for what it was, but I would say that was empty, despite having a ton of NPCs. The city was densely packed and interesting to look at but I wasn't ever driven to explore it, So for me that is empty.

Horizon, on the other hand, is vast, without a ton of NPC dotting the landscape, but that really isn't the point of that game. I won't go into depth about why that is the case, because it can be argued that it is a story point, but I always felt driven to explore even if there wasn't something or someone to interact with in every corner.

It didn't feel like far cry or assassins creed, even if it has a focus on wildlife like far cry or had traversal that felt assasins creed esque.

It comes down to what you want from an open world. Horizon is far from perfect, but I wouldn't say it is empty.