Its a perfect example because it proves that series that are popular online does not translate to success in the west. Both the anime and the manga failed in the US.
I don't think we're being strict at all, you just can't say something is big in the US based on such vague pretense like traffic over actual sales since traffic can come from anywhere not just the US. Honestly that is true for the most part since most audiences will not discover something unless its animated, OPM is a rare exception where its transition from successful manga to successful anime was seamless because it was already big enough online that most of its fanbase were just waiting for it to be animated and of course we already know that Heroaca benefited from Naruto ending which drew people towards it hence why its anime was so highly anticipated. The biggest manga online without a anime adaptation is Tokyo Ghoul :Re (which just got announced last week), Tower of God, and Goblin Slayer and this is just going by how they rank on manga sites.
Since when did the West only include the US...? Sigh...
The problem is you’re expecting a new series with no promotion outside of Japan to be on the level of big hitters, which just cannot happen with the manga market being as niche as it is. By that standard, nothing is popular atm, so naturally lower the bar a bit.
You have to compare how a series is doing relative to others in the same position as it. Does Neverland have a larger name in the West than a series like HZ? Absolutely. Does it have a larger name than most other series in it’s position
currently? Absolutely. Yes I’m going off website traffic, but so what? what else can you use when most of these series are yet to have voluem releases? Sales aren’t everything either, though they might be to the licensing companies. On their own, they’re a pretty vague reflection of popularity too. Theyre not the be all and end all of the name a series has built for itself. A series’ fame goes beyond just it’s official success, like you said with Gintama. Fame doesn’t necessarily translate to sales for a variety of reasons.
The TG franchise has already had exposure in the form of an anime, so it would be stupid to count it. Tower of God isnt even a manga and is a whole different ballgame, I don’t see why it’s relevant. Goblin slayer may have good sales (haven’t checked), but that certainly doesn’t mean it’s big in the West, you’d be hardpressed to find people who have even heard of it.
Though I feel like this conversation is getting nowhere because apparently something has to be up there with the most popular series in the west of all time to be considered “big” by your standards...