Because, as I mentioned in the exact same post you just quoted...
" it required a bit more effort to make full use of the system's capabilities, which was an extra bit of effort that devs weren't willing to go to if few people were going to buy their game to begin with."
The Wii has games that look much, MUCH better than COD. Metroid Prime 3 arguably looks better than any COD game on last gen, and Super Mario Galaxy, while not a realistic art style, was extremely visually impressive as well. The problem was that developers had to go additional lengths to get a good looking game out of the Wii, which was effort they were simply not willing to go to on a system where their game probably wouldn't sell that well to begin with.
if you think Metroid prime 3 looked better than any of the CODs then IMHO you dont know what you're talking about but that is your opinion. Good day.