Two points - next time you are just watching a varsity game, see how many times a shot isn't taken within 30 seconds. I think you'll be surprised at how this hardly ever happens.
Second point - we already have a shot clock. It's 8 minutes
OK - here's a third: I would support a shot clock if it eliminated the 10 second backcourt and 5 second closely guarded counts. Actually, I would like to see the end of the 5 second closely guarded no matter what. I don't think it's equitible to reward an entire team because one of their players stood within six feet of someone for 5 seconds.