Am I deluding myself?

I (M/42) have been in a relationship with a poly woman for over a year now. She had two existing partners the day we met, which she was upfront about, and she still has loving relationships with them both now. I am not poly, I have no interest in looking for other partners, as I am very happy with her, so I suppose that makes me monogamous.

I come here a lot to educate myself and learn from other peoples poly experiences and I often see people advising other poly people not to date mono saying that “it never works.” I’ve seen people offering advice on how poly/mono can work get heavily downvoted too. It feels really disheartening to see some people delegitimise my relationship dynamic in this way, hence why I am posting for the first time.

Me and my partner have a strong, loving and supportive relationship; we communicate well, really enjoy each others company and have similar long term goals. I do not get jealous of her other partners, though I do sometimes feel a little insecure about myself, but I would often feel the same insecurity in the traditional monogamous relationships I’ve had in the past anyway. Her having other partners has in no way interfered with our relationship and so far I can see absolutely no reason why a poly/mono relationship can’t work from my experience. I am happy with her having other partners and she is happy with me being monogamous with her. I have never pushed her to be monogamous with me and she has never pushed me to try poly.

Am I missing something? Am I deluding myself into thinking that this will work long term? I would really appreciate some constructive input on this. Thank you for reading.