As a pro mechanic I pretty much never spray degreaser at anything on an assembled bike. If I really need to clean a cassette while it's on the freehub body I typically spray degreaser onto my brush, clean the cassette, and floss off everything with a rag. If you're washing your bike it's pretty harmless to use a low pressure hose to wet down the bike and use mild soapy water and a brush to clean things, including the cassette, and rinse off with low pressure water. On my personal bikes I do very little drivetrain cleaning apart from when I more comprehensively overhaul a bike. Wiping down the chain often helps a lot.