There are many tourist traps in Japan, and I generally enjoy all of them. However, I despise Oshino Hakkai to no end.
I've been to Oshino Hakkai twice. It is especially bad because of over-tourism. Its over-tourism is because of the villagers' greed.
Hakkai literally translated into "Eight Oceans". They are ponds, not oceans. Stop bluffing and upselling it as something they are not. A couple ponds are so small that, the shadow from three people would cover up the entire pond. Not all nature needs to be turned into tourist sightseeing spot. Leave nature be!
There were too many people crowding the too little ponds. I couldn't see the ponds. When I finally squeezed through the crowd, the pond was full of tourists' reflection. I could barely see what was inside the water. Supposedly there were gold fish, blue fish, and green water plants. But no. All I saw was the rainbow-colored clothing from the tourists. Why would I want photos of strangers' rippling faces?
And who really counted the eight ponds? Everyone gathered at the main pond. There was no fence; people might fall into the water. Nobody cared about the two ponds farther away from the main site. For all I knew, there might be only four ponds.
The souvenir shops were the accumulation of the villagers' greed. The entrance to the main pond was located inside the big souvenir shop. The entire souvenir complex (from the parking lot to Oshino Hakkai, plus all the shops surrounding Hakkai) was larger than the eight ponds combined.
A person is not there to enjoy nature. The villagers want the tourists to spend money and get out. Don't look for the clarity and the serenity they advertised. Everything is fake and superficial.
At other tourist traps, villagers want tourists to at least understand a little about the culture, history, and tradition. At Oshino Hakkai, the villagers only want tourists to buy their crappy souvenirs; they don't care if the tourists actually see the eight ponds.