I still, to this day, have no idea why the writers turned Ross into such a jerk when it came to Rachel, because there are other times in the series where he's a pretty decent guy.
The main reason why he wanted to be a part of it because he is jealous of mark. and he is insecure since knowing that rachel is way out of his league. he is afraid that he might be going to lose her over mark or any other guy, hence the reason why he wanted to be a part of it. which is normal. it threatens him so much.
Writers just wanted to highlight characteristics of people who are extremely insecure in their relationships. Maybe even give a lesson to people of how bad it really looks by making us hate this fictional character
This is an example of relational dialectical tension. It's not wrong for a person to want to spend most of their time with their partner. It's also not wrong that someone wants to spend more time to themself. Different people have different desires and needs. This isn't Ross being "controlling," it's his own preference for what he wants out of a romantic partner.
Ross looks so unreasonably possessive and unreasonable. But that's the default position of our lives, if we are not aware of our deep seated insecurity and jealousy.
