Art hasn't really aged well. The story is its main selling point, but while the premise is interesting, the story usually plays into the oldest cliché in history -- desiring immortality because of human greed. Maybe 80% of the stories begin this way and doesn't change much in the process. There's always a character that wants to live forever because they want to become god or something similar. Worst is the Sun chapter that's basically a historical retell of the struggle between Emperor Tenmu / Tenji and themes of death, life and mortality is pushed into the background.
Characters are also usually quite unlikeable as they are usually reduced to personifications of greed, ambition, vindictiveness or some undesirable human trait. They have personal struggles esp. between good and evil, yes, but it is more often than not less prominent than their negative traits. They also usually fail to establish much significance since chapters are typically episodic and characters never appear again after their arc. Yes, everyone dies, but they are so unlikeable that the reader is very glad when most of them kick the bucket and fail to see the morality struggle and struggle between death and life.
The saving grace is Osamu's mastery of cinematic techniques and originality. Pacing is better than a lot of mangas today still, and stories are told with mastery of camera perspectives -- when a man despairs because they're stuck in an insurmountable hole, you'll feel the height of the rocky walls pushing down on you. The manga is also pretty refreshing for having an overarching theme, but leaves out repetitive story-telling; it is still about human greed 80% of the time but it isn't always X does this which causes Y and ends with Z every single time. The highlight of the manga for me personally is the immortal space explorer or whatever -- that he starts out as a simple human and comes to witness full evolution on earth before fading into the stars after a philosophical conversation with the Phoenix is a breathtaking experience not commonly experienced manga today, much less of its time. Mind blowing irony that he is one of the few who got immortality despite not wanting it in the first place. Just unfortunately imho, not all the chapters live up to the height of that particular story.
Don't regret reading it however to get one of the most hailed masterpieces of manga off my list.
