I can completely identify with this.
To me, there is a continuum between love and friendship, and it's a quantitative difference rather than a qualitative difference. This is confusing for me, seeing as most people believe that romantic love is "different" from frienship. I feel varying degrees of attraction to most of my friends, and feel love for a few of them. If I don't like my friends that much, they stay friends, but if I think they're awesome and a great person I naturally start feeling attracted. In the mono mindset, it's all of the romantic love for your partner, and none for your friends, which leaves me puzzled as to how I "should" treat my friends, or who I should be friends with.
Perhaps I'm only meant to be friends with women? For some reason even if I'm really close to a female friend, I never feel romantically attached. I could love her a lot, and I don't even find the idea of sex with a woman repulsive, but it always stops just short of romantic feelings. I really don't understand why this happens with women in specific, as opposed to men. I understand it's because I'm straight, but I don't get where the distinction lies.
Unfortunately, I don't really get along with most women anymore. I'm very rarely friends with girls, and if I am it usually isn't close because I feel that they don't really understand me. So if I was expected to avoid having feelings for other people, then I should only be friends with people I don't think are awesome? It seems unavoidable then, that I should have feelings for my friends.
But I feel like a relationship is when two people love each other and decide that they want to make it public knowledge that that's what they are to each other. With this comes the implication (for me at least) that they'll attempt to stay together and eventually build a life together. It's very expectation-heavy, and while that was fine with me when I was mono, it worries me a lot in the context of poly because of its inherently public nature.
For example, right now my mono ex and I still have feelings for each other and sometimes we do couple things, but we're not in a relationship. His best friend and I have strong feelings for each other and we act couple-y in private, but we're not in a relationship because that would mean making it public and that's WAY too complicated for everyone involved at the moment. If ever had feelings for a friend but didn't want to spend the rest of my life with him, I wouldn't consider it a relationship but rather a loving friendship, passing in nature. But people who do couple-y things with multiple people who they aren't in relationships with, what are they called? Sluts, right...? -shakes head-
To me, the relationship label is mostly for the public, and it also holds a promise for the future. It's a label of expectation... If it's fleeting, if it's shallow...why bother confusing everyone else by calling it a "relationship" when it clearly isn't going anywhere?