alt Hacker NewsNovelty is a significant driving factor here. Gen Thumbnails are eye catching because they are new and viewers haven’t adapted to skimming over them like they do with everything else.
Thumbnails, same as everything that is supposed to attract attention, have styles that change over time due to saturation and fatigue.
It’s the current iteration of the red arrow with a (staged) surprised face and as you’re saying we will all learn to just skip it as well. These things are always an arms race, and given LLM’s can only generate facsimiles of things I don’t see how it can stay ahead of it