This is exactly where I'm at. I've had numerous "romantic relationships," but I've come to realize that what I largely felt was friendship combined with some sort of sexual attraction. Any romantic feelings I had were fairly short lived and not all that dissimilar to how I feel about a close friendship (of which I've only had maybe two outside of relationships).
If I had to define romantic relationships both from what I've experienced from the people I was in them with and what I've observed from romantic couples I've known I would say it is like a friendship, but deeper. Every single person I've known who has been in romantic love (and this happens when I have an initial crush on someone) describes that rush and tingle you get in your chest when that person is around you, calls you, interacts with you in any way. It is a feeling that is really only reserved for romantic feelings, I get a similar feeling in my stomach for intense sexual desire, but they are different. I think there is also a sense of leading towards a bonded future together. Meaning marriage, or a marriage like intention to stay together, the possibility of shared children, pets, and assets. No, not every romantic relationship has this, but even polyamorous relationships have that in common, they are rarely just about friendship and or sex, they include an intention towards a loving future.
On the contrary, at least for me, a platonic friend (sexual or not) is someone I may want to be around, I may even chose to move to be closer to them, we may live together, etc., but they don't give me that tingle of love and I have no intentions of sharing a child, pet, bank account or anything else with them.
I think it's folly to try and define a romantic relationship without at least talking about love. Sure I can love my brother, I can love my friend, I can even love my dog, but it is different than being in-love and feeling like that other person is a literal part of me. I most closely identify as grey romantic and a bit lithromantic, so I think I basically understand what romantic relationships entail, but I'm not sure I've ever been part of one for longer than a couple of weeks, from what I've witnessed romantic relationships will wax and wane with respect to those feelings over time, but they all come back to those in-love feelings.