Ruby web dev here...I pretty much use liberal puts statements (actually the awesome_print) gem. It's never really been a problem for me with ruby. 2001-2007 I was primarily a Java developer and the debugger was essential. But since switching to ruby in 2007 I've just never felt the need. I think it's probably the cycle time...we were using BEA weblogic as our Java server and cycle times weren't quick so you didn't want to waste time and needed to be able to step through the code. With ruby/rails it's almost instant to see your logging so I've never even looked into how to use a debugger in ruby.
Another ruby dev, back in my java days I used debuggers from jbuilder and eclipse. I now use pry and much prefer it as an experience. I found having everything at your fingertips rather than scattered around a gui far more efficient.