is it a good idea to allow users to close questions easily?
Then when you want people to start closing questions? When we all have 200 rep? 3000 rep? 10000 rep?
We need to be able to close questions on sight since we need to shape our standards and what we want this site made of. If we wait and sit idly without doing anything things will get unmanageable and the site will perish.
How do you change wrong community rules if the people who made that rule can mark a question as dup and close it?
Bring it to meta and discuss it. Why you think some question should remain open/closed? Expose your ideas, just not bash out some believes without specifics cases that we could discuss constructively.
Doesn't it limit too much the freedom of expression?
You move to a communal house, sharing a roof with different people. We share cost and expenditures of the house. There are more people living there. They all agreed on some terms that were explained to you before you moved and until you accepted them you couldn't move in.
You think you are being limited your freedom? You agreed with it before hand. You should already know the house rules and you should know that to change it you need to discuss it with the residents. You can't just walk in, throw a tantrum saying that everything is wrong without identifying any specific problem or propose a solution. What gives?
BTW, you are still a kind of visitant here. You first have to observe what do romans do so you can speak about improving it.