Is 'Related Words' a little bit broken?

Not wishing to call up an online thesaurus, I highlit the word ‘complex’ and used the right mouse button to look up ‘Related Words’ with the intention of finding a synonym so I could reuse the word ‘complex’ in a better sentence.

Oh dear.

Somehow I was offered ‘feeling’, ‘compund, chemical compound’, ‘whole’, and ‘structure, construction’.

So is Related Words not a thesaurus function? Is there a way to link up to a better thesaurus?