Who is being excluded? If anything the complaint I keep reading is that too many people are being added who have no business being there (e.g. Steve Bannon).
Chairman of Joint Chiefs of Staff and Director of National Intelligence are no longer permanent members of the Principals Committee (the actual subgroup that has people so wound up); effectively, they only get to attend meetings when they're invited (the wording is something along the lines of 'whenever their expertise is a topic of the meeting'). Since this is the National Security Council, people think it's weird that they'd have any meetings that wouldn't be in the purview of the military or intelligence communities.
Sean Spicer did explain this as a situation where both of those members were not excluded from meetings and could attend any meeting they wanted to, just that they were no longer required to attend every meeting.
As long as that's true and so far there hasn't been any reporting to say it isn't, I don't see the issue.
