LWers are often against minhagim that were established due to factors that are (at least in their opinion) no longer relevant today.
That’s the point – that those factors are no longer relevant today. I grew up eating peanuts on Pesach, and I clearly remember my Mom z”l using peanut oil. You cannot convince me that some time between the late 60s/early 70s until today that peanuts magically became kitniyot.