Not all people taste food the same way. Some people don't have a strong sense of taste, so eating Soylent all/some of the time is just not a big deal to them. Just the same as how some people are tone deaf, so music is not important to them. Or colorblind people can't tell the difference between red and green, so stoplights aren't a big deal to them. Wait a minute...

But really I think a lot of the Soylent hate comes from the fact that people assume their own senses are the best judge, when really we only have a sample size of one. It doesn't even have to be a lack of sense acuity as I said above, but just personal taste. People come in all different types, and that's cool.