Subject: What are the disadvantages of Astronomical Spectroscopy?

Are there any disavantages/difficulties in Astronomical spectroscopy? Are 
there certain things that cannot be seen or found out from this type of study? 
Are there setbacks or problems? For example, do we get more/ better 
information about the universe by observation with a radio telescope instead? 
Is spectroscopy ever impractical, dangerous or too expensive? Do other methods 
have advantages over astronomical spectroscopy?

I am interested in any setbacks in this type of study, such as, high cost etc. 
Anything really.

Thank you for your help

Re: What are the disadvantages of Astronomical Spectroscopy?