In well functioning product teams everyone should be working together to make a better product, recognising the roles and strengths of each other. If this isn't the case, then your org has bigger problems.
That's rarely the top priority for everyone on the team at the same time. Design folks want to 'design', and agreeing that 'feature X' doesn't need to be in the screens - even if it's "the better product", doesn't align with their career need to have showcase material for the next job interview.
Similar with tech/dev folks - an update feature might just need simple poll mechanism, but that doesn't give them experience with building a full pub/sub scalable architecture platform, or testing out the newest messaging libraries.
The more people on that team, the more conflicting priorities there will be.
This doesn't sound like a great team, and doesn't really align with my (sure, admittedly limited) experience. I've only really worked once with someone who had strongly personally motivations that worked against the teams goal, and it was recognised that they were a wanker.
That is completely true. To work together to build a product, to have everybody understanding what is what needs to be achieved, and collaboration in general is the way to go.
In organizations where business does not trust engineering, engineering does not trust design ... things are never going to work. It is a collaborative effort, one point of view is insufficient to create an attractive product in a cost-effective way that is not full of tech-debt.