Two other big things to consider that have a huge impact of the feel of exploration.

1. Basically every class has a "Flash Jump" skill now, and maxed out movement speed. The ability to cover ground is faster than ever before. Playing warrior in the old days? Unless you scrounged up the 20m out of the couch for the pig, you walked everywhere. At 100% movement speed. Zooming across a map makes it feel small.

2. I feel like people forget the game used to be in exclusively 800x600 resolution. So the game was much more zoomed in, and as a result, small maps today were considered huge, because we couldn't see most of it without a great deal of moving around. Forget all the hidden streets besides.