That's not Bundler's fault. It's the fault of the person who made the versionless Gemfile.

There's really no comparison between using Bundler and mucking around with JAR files or Ant scripts in Java. I've even seen Python codebases with a Java-esque rats nest of dependencies that are just as painful to get setup correctly.

Bundler is way easier. I've never been on a Rails project where it took more than 30 minutes to get the env setup and it's in large part, thanks to Bundler. Admittedly, I haven't touched Java in a few years, but last I checked, Java had nothing like Bundler (which is a shame, because it could really use it).