The problem with that is that Bejing makes it very clear that declaring independence would lead to an invasion of Taiwan. So for a long time most Taiwanese rather did want to keep the current basically independent status quo. However support for unification was low since Taiwan became a democracy. Since the Hong Kong protests and the extraction bill polls for independence show a majority supporting it though.
Also Palestine has a seat on the table, just no vote, as a observer of the UN without being a member.