In fairness Japanese pop culture is stained by cheap mass products like YuGiOh or Beyblade... The product advertisement anime series are just getting worse which each season. These kind of stories give the whole market a bad reputation.
Several things are also hard to translate into western culture as people in mangas are behaving in not western ways for obvious reasons. This alienates many viewers. However, if something is heavily americanised you can`t sell it anywhere else as the rest of the world would just be annoyed. In fairness I have watched Dragonball in German, French, Japanese and even Italian but I can`t stand the American version. The soundtrack is often too loud and the whole show is much louder than for other markets and is also extremely censored. The product needs therefore multiple localisation to be suit the needs of the viewership in several markets.
Localisation is an issue due to language barrier. There are not many gifted writers out there who can translate the Japanese original and convert it in an interested way. However, many items are just lost in translation even if the language is using the same puns but they won`t have the same cultural knowledge. f.e. Europe has a man on the moon and not a hare.
It is also confusing that some stuff is just translated in items the audience knows. Sailormoon has never eaten any rice balls on German television even if you see her holding something in her hand which doesn`t match the translation. This can also cause at some point confusion in case not the same translation was chosen.
The good mangas are intended for a mature audience. These kind of market is a niche which only a few US and European readers recognise as such. It is part of Western culture that adults prefer books over comics.
Japan also doesn`t do much effort to export culture. Keeping centuries of isolation in mind it is still a country which has issues to open itself. Japanese have also issues adapting other cultures which makes it difficult to negotiate with Japanese if you don`t want to adapt either.
See also the pricing for the things... When I was a teen I could afford to get hundreds of pages (we got in Germany in the 80s and 90s several issues of US comics in one cheap issue) of comics for my pocket money. (No, I haven`t received much) The comics nowadays are just 20 - 39 pages strong and cost the same amount... This has also raised the price of manga comics which makes it less attractive or me.
I reckon these are some of the reasons why Japanese comics aren`t as successful outside of Japan as they are over there.
I still like some authors like Katsuhiro Otomo or Yoshito Usui....
However, beside these authors I consider most manga to silly for myself and prefer a live action adaption like the excellent Thermae Romae 2.
I might now also shock the audience but I also had some hard times liking Attack on Titan... but I still want to see the movies... Well, maybe it is my age.
