I would agree on some of your points : few minutes initialization times and 1-2 GB heaps may sound not that bad, and when we are talking about product that just provides a fancy, over engineered way to run bunch of shell scripts (considering jenkins doesn't integrate sandboxing from the box) ... honestly there is no excuse to spend 2 gigs of ram just to run shell scripts with web UI. It would be much better in a long term to improve energy/resource efficiency of software like this, just to make it more sustainable and reliable.

Edit: configuration-as-code feature is available in jenkins 1.x with job dsl plugin [1], I'm using it at work, because managing 50+ jobs by hand was just insane. Nowadays we just have few dsl files :)

[1] https://wiki.jenkins-ci.org/display/JENKINS/Job+DSL+Plugin