I agree with and know that a lot of what you said is correct. For me, it’s just much easier to supplement omega-3 than it is restrict omega-6 across my entire diet. That convenience is really valuable to me. I do a generous tablespoon of ground chia seeds stirred in water daily for my omega-3s, as opposed to a capsule.
Also, if you’re a vegan, there are somethings you should probably take via supplements, B12 being the most notorious example; pretty much every vegan (and many omnis) should take B12 supplements. (B12 is produced by bacteria and doesn’t occur in plants.) Being supplement-wise is important as a vegan. There are a lot of scams out there, but avoiding supplements altogether is ill-advised and in the case of B12 likely deleterious to one’s health.
Edit: There aren’t citations to this but the reasoning is pretty sound; for anyone interested in more discussion about the value of supplementation for vegans (they’re pro): philosophicalvegan.com/…/Natural_vs_Supplementati…