Given that the UK chart is pretty static with Call of Duty, Minecraft, Fifa, GTA and first-party Sony/Nintendo stuff, Bravely Default landing at no.11 here is not a sign of anything regarding the series, I'm surprised it registered at all. The previous games didn't do well either, JRPGs rarely do, let alone those with roots on 3DS.
In fact, Bravely Second made it to 12th on it's launch week in the UK in 2016, so if anything, in terms of positions its a mild improvement :D At the time it was also the highest-selling release on a Nintendo platform that week, but the WiiU was dead and the 3DS was struggling, whereas now the Switch evergreens in addition to the usual big hitters make it even harder for a JRPG to register. Anything that isn't a major AAA release isn't really going to shift the U.K. chart and that's not a new phenomenon.
en.wikipedia.org
Suffice to say, putting its consistent launch sales (digital will be an increase) down to 'art style' for not lifting those numbers higher is quite the stretch. Just wishful thinking from someone thinking their personal subjective dislike extends to barely-connected sales trends worldwide, let alone two countries with wildly different charts (outside of some of the Switch evergreen stuff).