Yeah. Presentation as in, more kid friendly and medieval? Yeah. It has its place and I refuse to accept that a game that looks like this

with Akira Toriyama art, the creator of one of the most popular properties to ever come here, has no place in America.
To me it is objectively good looking in its aesthetic. But hey, that's me.
This?

I would understand. But not XI.
Especially given one of the famous exceptions you posted about above looks like this.
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Your conclusion is inherently self defeating.
The real reason DQ hasn't "taken off" in the US is:
1. DQ7 was ugly as bricks and came out on ps1 in a time when everyone was getting used to DC/PS2/GC/XB graphics. Awful timing and took fucking forever combined with the fact it was ugly as sin. I love the game and even I think it has absolutely no aesthetic value.
DQ8 managed to do really well in the west and introduced an entire new generation (aka me) to Dragon Quest. They decided to...
2. Put its sequel on handhelds. Western game enthusiasts are not keen on handhelds like they are in Japan. Handheld games are far more niche and many people who bought and loved VIII didn't show up for the next one or the remakes for that reason.
3. X was an MMO that didn't come out here.
4. Long gaps between games. There wasn't a single DQ released between IV and VII, which was a 9 year gap. And IV itself? It came out on the NES in 1992. FFIV came out that same year on SNES. Between IV and VII other rpg series moved in to capitalize, notably Final Fantasy. Square properties got a dramatic representation on the Super Nintendo, which was the main jrpg system of its day. Not only was DQ's last entry to come out in the US in the 90's a two year old game released on aging hardware, but it skipped out the entire rest of that decade and pretty much the entirety of the ps1 era. Its name brand suffered as a result and they had to rebuild that brand from scratch.
5. DQ continuously has to rebuild its brand in America because of all of these missteps. VII had to rebuild because it was the first entry since 92. VIII had to rebuild because VII was released on aging hardware and looked like vintage shit even at release. IX sold well
because of VIII[/i] and the Nintendo marketing. Now XI has to rebuild after 10 years of being on handheld and skipping an entire entry. Therefore, the health of DQ in America isn't just based on XI but also XII if it comes here.