I'm not familiar with all the details of RFK Jr's position, the public debate about it, nor how many of the things reported in the news are accurate (truth being the first casualty of politics).
But I just looked for those topics in the official Make America Healthy Again report [1].
The positions in that report on those topics were not so unreasonable. It says seed oils are a concern because they are ultra-processed fats, only mentions cholesterol in the context of PFAS, and says "vaccines benefit children by protecting them from infectious diseases" but we may not need to give children nearly 30 doses of them.[2]
I do think his general position that processed food is unhealthy is not only reasonable, it generally matches conventional modern medical thinking, even if he is wrong about a few details.
And of course people looking for political ammunition only look for details they can use against him.
1: https://www.whitehouse.gov/wp-content/uploads/2025/05/MAHA-R...
2: https://www.cdc.gov/vaccines/hcp/imz-schedules/index.html