My personal opinion on Mfauli is that it seems he has a harder time with suspension of disbelief, which may or may not impact how much he enjoys whatever anime we discuss. Sometimes I think it's silly for whatever reason but I've had this issue with some shows as well for example 'Your lie in April'. It made the show worse for me since I couldn't just flip a switch to suspend my disbelief and immerse myself in comparison to everyone else who seemed to have loved that show.
Another thing I can think of is how much people believe in the government/police varies impacts our view of how likely this is to happen. So while I don't doubt it could happen I'm more with Mfauli on this, you expect me to believe that the government/social service helped him bury his dad and then didn't try to place him with a foster parent/orphanage? In modern Japan? This isn't a youth getting trafficked into servitude to organized crime, it's a child that turned into an orphan which should by default be protected by the government/child protection service/social service/whoever handles these kinds of thing.
Though I can close my eyes to it and just accept that it happened in this show to make Denji have a pitiful and sad background while giving him an excuse to be stupid/lacking. But if Mfauli never brought it up I wouldn't have thought about it at all and just accepted it and in turn never come to the conclusion that the issue isn't Denji, it's that the government didn't try to help him and was ok with an orphan living on the street right after their one and only guardian died.
Blaming it on Denji however is victim blaming, blaming all the people who should have helped and should have prevented a child from ending up in that situation however is fair game imo. And should something like this happen in a place like Japan it's 100% the government failing to help vulnerable children they should have been protecting.