It's kind of hard to approach this in a tactful way. I think a lot of why vegans don't appreciate this approach is because it often doesn't work in actual practice. I'll give a personal example as an analogy - I used to be a smoker. I tried quitting at least 50 times over the time period I was addicted to nicotine. One of the tricks I would use was to reduce the amount I would smoke each day. It would help briefly, but what would always happen is that I would get to a point where it was too hard to reduce any further, and then after plateauing for a few days, I would rebound and smoke even more than I used to.

Reduction still played a role in my effort to quit, but there were a lot of other tricks I had to employ to make it stick, and the overarching point is that reduction as a goal went nowhere, but reduction combined with the intent to stop all together did eventually work.

And that's what also happens with dietary changes. Reduction starts with halfway good intentions, but when it's the goal it becomes a temporary self-soothe that simply ends up rebounding in the end. In fact the people who run wfpb health coaching clinics have stated in interviews that people are most successful when they go all in with the dietary changes - because it turns out that people often feel dramatic positive changes to their health within only days of going plant-based, and those positive changes reinforce their motivation to keep going.

And as this article points out, reducitarianism can never achieve justice. It's like when suits-wearers promise to reduce their carbon emissions by 10% by 2035 or something. It's better than nothing, but will never solve the problems that need to be solved.

https://www.surgeactivism.org/reducetarianism