Using simple software needs not as much resources as complex software. Therefore you can use a computer for a longer time period. Using a simple operating system with simple programs is no problem on a 10 year old (or even older) computer. This means, simple software is a direct contribution in the fight against climate change - and it is good for your wallet

Our criteria
The tools listed here should be
Rating
In general from + to +++++
Lightweightness
Simpleness
+++++ extremely simple (e.g. one small file of code)
++++ very simple (a small number of files with modular code)
+++ somewhat simple (a mid-sized project, but manageable and reasonable modularized or consists of several small tools)
++ Not so simple anymore (big project, but manageable for a small team)
+ Complex (a project with high complexity, not manageable or understandable by a single person or a small team)
Easiness
+++++ Very easy to use by novice users
++++ Easy to use by novice users after reading documentation
+++ Easy to use by users with basic knowledge and after reading documentation
++ Usable for experienced users after reading documentation
+ Only usable by experts or after extensive study of the documentation or after a training course