I'm an E5 iOS at a Big Tech company. I'm in the process of switching teams. While they're figuring out the paperwork, I've been invited to their roadmapping and architectural discussions.
The 2 E6s are dominating the discussions. The E6 iOS has been on the project since its inception a year ago and has all the context; the E6 backend has been helping out our team with the discussions and may eventually join our team. I'm the newest team member so I have the least context. The E6 backend's proposals usually sound like great ideas to me, but the E6 iOS often shoots them down and provides historical context on why those are bad ideas.
In my 1:1, my manager asked me why I'm not participating in the discussions. When I told him I don't have context, he told me to participate anyway. How do I participate effectively when I don't have context?
Ask questions! A "trick" I like to use is to restate key points from the meeting and see if I got them right - I break down this tactic in depth here. If your team has E3s and E4s, I'm sure they're also struggling if they partake in these meetings - Clarifying information via questions will be a huge value add to them too!
It seems like the discussion between the E6s on your team is very juicy as well - I would be taking thorough notes if you aren't already. The historical context from the E6 iOS in particular is extremely valuable. In general, it is very important to understand how engineers (especially more senior engineers) shoot things down, both in system design and code review. I would look for patterns in what the E6 iOS is citing to block proposals and make them more technically responsible with the goal of playing that role more in the future.
I also recommend going through my System Design series if you haven't already. I'm also a mobile engineer, so that series has a lot of mobile-specific design principles. They may provide some ideas on how you can contribute to these discussions (which may include shooting other things down, haha).