Very cool. My wife is from Taichung. Her parents built a house on the outskirts of town in the early 1980s. It was the only three story building around and had a clear view of Toko-kei river from the east side. It now has a clear view of a ~10 story building inches from it. The river is a long green park. And the city seems endless.
Yeah, a lot has changed indeed, and I'm not surprised that many things were "better" before. Population density rise takes its toll. The endless cities are indeed a thing, wouldn't be totally surprised if the plain on west side of the island would become a sort of mega-city spanning the entire length.
Seems like river-relocation is also a quite common thing (see e.g. Taipei's Neihu area in the NE, bunch of smaller examples too).