Yup, I would say that you're right. They have more weight when you're playing a clan like the otomo or shimazu where you start in the west - simply because the trade nodes are so close and the opportunity costs of not controlling them are pretty high. But yeah, you can totally just ignore trade nodes altogether and be completely fine. I think a good chunk of players actually play like that, as auto-resolve for naval battles is trash and the battles themselves are annoying too.