Complex sentence: The low aspect ratio of square rigged sails (usually 1/2 to 1/3) produces much drag for the lift (motive power) produced, so they have very poor performance to windward and they cannot sail as close to the wind.
Split into simpler sentences: The low aspect ratio of square rigged sails (usually 1/2 to 1/3) produces much drag for the lift (motive power) produced. So have very poor performance to windward and they cannot sail as close to the wind.