You stop comparing like with like
At first it feels efficient to keep everything on one screen. Then shoes are sitting next to knitwear, bags are mixed with watches, and you stop making clean comparisons. The page is still moving, but the decisions get worse.
You save things for the wrong reason
When a page gets too busy, it is tempting to save anything that looks halfway decent because you might not find it again. Later you are left sorting through a pile of maybe items.
That is a good sign to stop, back out, and open the category you actually care about.
You miss the obvious weak spots
Dead links, thin photos, unclear sizing, repetitive descriptions. None of that is subtle. It only starts slipping by because you have been scanning too fast for too long.
If that sounds familiar, take the next click more seriously. Open the categories page, or if you are unsure whether the big list is still helping, read the comparison page.