What are the set of core tools/functionalities in Adobe CC products one should learn so that it’s easy to migrate to any other alternative software?

What are the core toolsets/functionalities in Adobe CC products e.g. Photoshop / Illustrator / After Effects etc. that one should learn so that it's easy to migrate to any other alternative software such as Krista / GIMP / Inkscape / Blender ? Learning an entire software is probably not possible. Hence learning the core concepts would help in the long run.