Hello, and please note that the animes mentioned on this list are all philosophically driven. They may cause uneasiness while watching them because they make us introspect on our ideas of how life is/should be accompanied by complex abstract questions that often don't have answers.
On a positive note, these animes will introduce you to new and unique perspectives as you'll be shown the philosophies of others and learn how they perceive the world. Due to this, you may inherit some of their thought processes and learn to empathize with their reasoning, which further develops your own theories and understanding of the world, human nature and the purpose of our existence, assuming there is one.
On a negative note, many of these animes will take philosophical concepts and blow them out of proportion to force the message or make it obvious.
Consequently, many of the animes on this list will also be uncomfortable to watch, and I will add warnings in their summaries. So, if you're a sensitive individual, please prepare yourself mentally before watching any of these animes, as some thick skin may be required at times.
Viewer discretion is advised.
Lastly, a majority of the animes on this list fall into these genres:
Avant-garde
"Dementia"
Psychological
stack
Anilist Sync