One-sided relationships are not good for anybody, especially for the person whose interest is not reciprocated. That can be applied to romantic relationships, friendships, and whatever type of bond you want.
When we form a bond with a person, we sign an unspoken contract to be nice, respectful, and honest to one another. When one party doesn't commit to it, that's when the relationship starts failing, and trust disappears. It sounds dramatic to put it like that, especially when the relationship is not as close, but that is the point. When we start treating every connection as expendable, that's when we start losing them and seeing that it's very easy to be left alone. People need to feel appreciated to stay around and put effort into maintaining the relationship. When that doesn't happen, they leave, and they are entitled to it. I have cut off friendships myself when I realized that the other person didn't value my friendship as I did theirs. It is not wrong to set boundaries and dismiss people who are not good friends. When someone lies to you, treats you as a second choice, and then expects you to rearrange your life for them, all you have to do is politely refuse and consider the relationship terminated. That doesn't mean that from now on you're going to be mean or impolite to them; it just means that you will no longer count them among your close relations, and you'll treat them as you treat every other acquaintance you have.
What would you do if you had a friend who didn't prioritize your relationship? Would you set a boundary, or would you let it go?