I hadn't thought about if I've seen an electronic device, computers or smartphones and if these things are nonexistent it makes it a lot more believable for me that no one knew about Denji/government not doing anything.
Spoiler?
I actually googled it since you said it gave you cold-war vibes and the story takes place in the 90s so it makes more sense to me that they missed taking care of him. Anyway I stand corrected, you were right with your observation and it's not actually weird anymore.
They have a lot of surface level similarities, if you check deeper obviously there's going to be differences but it doesn't make my statement that they're both part human part curse/devil and they're both being monitored and both on death row any less true.