Were you coming into this relationship with the understanding that you would be in more of a "secondary" role? Regardless, NO ONE deserves to be laughed at!
I stepped into an established poly MF relationship with the clearly stated and agreed upon expectation that I would be treated as another primary...never a secondary. It never happened. When I would raise similar concerns to your own about not feeling included in decision making, having my opinion heard and taken into consideration, and/or wanting a commitment from him/them to spend more time together with him/them/extended family, e.g. once a week minimum, I was told I was "too needy" or often ignored and told I didn't seem to understand poly relationships very well!
I eventually chose to leave the relationship as I knew I wanted and deserved differently and better. It's been a year now and I still miss him...her....the extended family. But...NOT enough to compromise what I want, need and deserve.
Yours is not a new poly relationship. You've been together for 4 YEARS. If the excuse is that he needs to give her more time, attention and consideration to "reassure" her....I can't imagine that she will ever be reassured enough!
Please take good care of yourself as you make a decision about what you want to do. You deserve to be treated minimally with courtesy, respect and kindness.