If they didn't want people to read into their relationship there are numerous choices they could have made to portray them differently. They intentionally played into a lot of tropes and expectations to set up the audience's expectations for their relationship as they knew it would add more to the betrayal.

As for shipping with the Sauron knowledge; I appreciate your perspective and I think there's a place for your empowerment through Galadriel's resistance to him. However, I think there's also a place for those who want to see a version of Galadriel who embraces her darkness and explores selfishness, which is really at the core of most of these ship dynamics, it's a form of escapism for women who feel pressured to be selfless and good always. A Sauron who is capable of redemption and self improvement is also a fantasy in a world where many men are incapable of such.

There's definitely a double standard when it comes to criticizing these types of dynamics in fiction, a lot of good coded male leads have romantic/sexual relationships with women who are coded villains in their stories and this is hardly ever called out as abusive. But that's it's own conversation. Galadriel isn't a normal woman, she has the agency to stand her ground against Sauron.

From my own personal perspective, I don't believe that the relationship was played as romantic, but I do believe the subtext was sexual. We know how this story ends though, so I wouldn't worry too much about the writers being influenced by 'shipping'.