"All the decisions are made in Brussels"

The decisions made in Brussels are those that affect all EU countries. You might as well say "why should MPs from Cornwall and Leeds and London be making decisions about things that affect me in Norfolk?" or "why should councillors from Kings Lynn and Great Yarmouth be making decisions about things that affect me in Diss?" The question to ask is not "where are decisions made?", but "are decisions made in the right place?" 

If your answer is "no decisions should be made abroad that affect the UK", fair enough, but you can't stop it happening, even if we leave the EU. Europe is our biggest market place. We will have to make goods that comply with their standards if we want to sell to the continent. Decisions made in the EU about those things will continue to affect us, but outside the EU we will have no say, however hard we negotiate. 

What people often mean when they talk about decisions taken at the European level, is the Human Rights Act. Britain has been signed up to the European Convention on Human Rights since the 1950s, when we helped to write it. It has nothing to do with the EU, and leaving the EU will not change the application of the convention to UK law. 

The arguments about the Human Rights Act are for another place, but consider this one point: If Britain abolishes the HRA, it is my human rights and your human rights that will be abolished.