Pimcore was awesome, it was clean, considering the alternatives - it was a basically a dynamic objects store which would load dynamic blocks to generate content and theming on the frontend - and editable blocks in the admin panel. It was so relatable from a webdev standpoint, and very "hackable" - I loved it.
The idea at that time was so appealing (mind you, afaik that was before React or even Angular. Jquery was a thing at that time and ExtJS, Pepperide Farm remembers...). Now it gotten much much bigger of course, but in the beginning, it kinda reminds me of this: sleek, extensible also very relateable. Definitely not made for the size of a multi billion dollar franchise, but fun to hack around while still maintaining relatively clean code.
[1] http://web.archive.org/web/20110606024114/http://www.pimcore...