>>12279568Lack of variety in encounters
Constant encounters like caves
Usually quite open so requiring you to move around a lot to make sure you cover it all and don't miss anything.
All this combined means you're surfing back and forth a lot, getting constant encounters all of the same pokemon. Repels are an option but are only required because the water routes are bad, it doesn't make excessive water routes not bad, just gives you a way to manually fix the negatives.