He isn't a king and that is not his responsibility in the American government. Creating and passing law is the job of Congress. The president only has the last say on whether it goes.
Democrats are not "in power." It's been a split government since the second Obama term. Democrats do not have a majority in both houses of Congress.
Even when the democrats do control both houses, as with the first Obama administration, they do not force the issues. They operate on a "we don't stoop to that level" policy which is why liberal voter get upset with them.