ES doesn't come anywhere close to a masterpiece, mainly due to flaws in the plot (plot holes, plot armor) and in the characters, notably their lack of depth.
In terms of plot, ES falls short due to its premise. Shuro's power is non-interactive: he goes into your mind and can kill you or brainwash you. This is nothing short of being OP, and if he enters someone's mind, there's no real telling what's going on until the narrative fills us in. So where could this manga get interesting?
In the characters! That's because now the question is, how will he use his powers and how will humanity respond? Unfortunately, the characters are simple and one dimensional, and especially serve the inconsistent plot before serving themselves. Shuro initially stands out as curious, nonchalant, not emotionally invested in anything, and does some good deeds when he feels like it. However, as the story goes on, he loses a lot of complexity and gets a side role. His emotions get simplified and he very quickly becomes a sensitive person.
Psychology is oversimplified and most of the characters' intentions are induced as originating from some traumatism, notably lack of parental love. This is similar to Freud's psychology, which is so outdated and pretentious hand-waving that it's not even taught in standard university psyc textbooks anymore. [As a minor note, characters are also overly polite (but maybe this manga is juste more Japanese-like than others). When Mine accuses a woman of beating her child, that same woman, regardless of her anger against Mine, still lets Mine into her house on several occasions... There are other instances of a character hating another, yet acting way too friendly, even more than you would act towards a typical friend. ]
Finally, to seal the deal on this 5/10 rating, ES has your dose of poorly written plot. Characters experience plot armor all the time and there are significant plot holes (specifications below).
**(SPOILERS section)**
Plot armor happens for both Mine and Izaak. When Mine is surrounded by brainwashed police officers, Shuro comes to the rescue (although he was not initially with her). When Izaak is about to get shot, Mine gets emotional and purposely misses his head. Then as he retaliates, Shuro yet again appears from nowhere to save her.
When the author realizes his story is spinning in circles, the story-writing suddenly gets incredibly rushed. Izaak turns out to lack antibodies against aging, so he's suddenly grown/aged to 70 years old. The problem? Shuro is 15 years old and has grown to the human equivalent of 20-30 years old, looking like a "handsome college student". We thus understand that ES age around twice as faster as humans. So why would Izaak, who is the human equivalent of 10 years old, grow much faster than Shuro and age more abruptly? Over ~2 weeks he suddenly gets white hair and his skin gets wrinkly. I'm pretty sure aging is a spectrum; if he were lacking the antibodies at birth, then he would have gotten wrinkly and gray hair progressively.
The young girl (Yuri) somehow becomes vulnerable to Izaak's power and gets killed off, even though she's supposed to be some kind of "race" with immunity to ES powers. The author could argue her 'inner will' was weakened after her mother died, but are we really going to say that this 4th grader, when not in turmoil, has a stronger 'inner will' than all those adults that have died from ES, from delinquents to researchers? If so, then the author did a poor job at showing us that those who could die from ES were weak-willed humans.
Finally, the final battle. As I said at the start of this review, these battles mean nothing to us and the author even took advantage of that by deceiving us over who won. Then we got the dumb magical ending where Shuro's powers transfer to Mine and that she surpasses his ability by killing Izaku...
