Some people recognize the great wrong of animal exploitation, but think that veganism is extreme. They might instead advocate for vegetarianism, or "flexible" veganism, saying that we needn't avoid all animal use, just most. Because they perceive it to be difficult to refrain from consuming animal products, or finding vegan alternatives for clothing or hygiene products, they think the "extreme" position of veganism is onerous and unnecessary.
This rests on a mistake. If you come to see the ubiquity of animal exploitation, this means that the problem of animal use is extreme. That billions of sentient animals are brutally tortured and killed, and then endlessly processed into products offered up for our consumption sounds like an extreme dystopian nightmare, but it's true. This means that the response, veganism, ought to be extreme as well. How could the appropriate response to such egregious wrongs not be extreme?
Which is not to say veganism is difficult, in a day-to-day sense. Once you realize what you need to do to live a vegan life, you get used to it quite fast. You'll learn that though animal products are everywhere, there's also vegetable-based alternatives that abound as well. And once you really grasp the injustice at hand, it's no challenge to become sufficiently motivated to go vegan. But there is certainly a sense in which you are rejecting much of what our society to produces, which is an extreme step to take. And that's exactly why it's required.