I don't think attachment denial is a great way to relate
Relational liberty is not a pious apathy
One thing I often see amid the many streams of memes is that non-monogamy somehow grants people superpowers of choice - you don’t own anyone you are with, and you don’t get to take them for granted, so your intimate relationships become super-valid because every day that you and yours show up together is a product of conscious intention.
I think this is lovely, partially. Showing up intentionally is great, and living without the relational guard-rails of monogamy can force a whole lot more intention into your life since there’s just way more to think about and talk about when everyone’s dating multiple people. This kind of intentionality is fairly neutral - it can be very illuminating and disclose a lot about who you are and what you want and enlarge you as a person, and it can also be a lot of effort and very anxiety-provoking and leave you feeling like you always have to be on high alert since you never know if your partners will evaporate from your life tomorrow for whatever reason.
Of course everyone can evaporate from each other’s lives tomorrow for whatever reason, due to brain damage or death or just sudden and extreme loss of interest. As I see it it’s a fine and worthy thing to explore relating with people where you feel fairly nonchalant about the connection, where you’re happy to have it while it’s here but if they lose interest in you or leave you for someone else then you feel supportive of them and not to terribly injured by the experience.
I also think that there’s something important to be said about attachment, about creating committed and invested relationships where there’s some shared understanding that the relationship itself won’t instantly evaporate and that some measure of depth and connection will accumulate beyond what any party could conjure as an isolated individual. These are relationships where two or more people are creating something bigger than themselves - entering into the relationship isn’t a matter of giving up some part of yourself as much as creating a new self, a larger self that’s a part of a bigger unity.
These aren’t the only valid kinds of intimate relationships, but they are valid ones, and I think it’s foolish to celebrate an absence of attachment as some sort of achievement. By that, at least, I mean that I could never do it and I think people who do so are doomed to loneliness that becomes difficult to acknowledge the more pious you get about it.
Non-attachment relationships can grow surprisingly and painfully into attachment relationships when one or more parties wake up and realize that suddenly the idea of life without each other has become a terrible thing to consider. People might have somehow graduated from a cell on a spreadsheet to a vividly-particular human being. It can happen even despite our conscious intentions - human relating is bigger than our capacity to theorize, something we all have to learn how to do the hard way, with most of the deepest lessons coming from painful loss.
So: be conscious and intentional, and be patient and kind when life and love surprise you with feelings you could never have been conscious and intentional about. It’s ok to see relationships as being fleeting moments where two billiard balls collide and bounce away from each other, sharing some energy and changing trajectory but otherwise staying separate forever. I also think it’s always worth it to be open to something more.