Not all of the miners are blocking changes. If most of the nodes accept a change these nodes can ignore new blocks that do not flag support for the change. This way the nodes can create economic pressure to miners blocking changes.
Correct me if I'm wrong, but for big mining companies running enough nodes to ensure their interests is a fraction of their entire investment. So I expect miners overrule existing node count if sth is against their interests.
The node count doesn't matter in this case. If a miner runs thousands of nodes he can relay his own block within his node pool but he cannot force any other node to relay/accept this block.