Sure inbreeding is bad, but definitely not as bad as some claim it to be.
Risk of complications is higher, certainly enough that it warrants attention,
but definitely not to the point of making generations of incest impossible or highly unlikely to succeed.
As for mindset, culture matters alot when it comes to what mindsets people develop.
Personally don't think I ever could view my sister as a potential partner..
Hell, I still haven't managed to stop viewing her as a tiny lil girl even,
despite that objectively she's definitely been nowhere near tiny for the last ten years atleast.
(Passed me in weight like fifteen years ago or something, and not that far from me in height either.)
Well, limiting yourself to those outside family really aint limiting at all,
and if that's enough to improve chances of avoiding complications even a tiny bit..
Definitely worth it, something the vast majority would agree with I believe.
Could further improve chances by limiting yourself to "interracial" relationships,
but that would be severely limiting so.. Doubt many would readily agree and live by that.
(Not to mention that people often feel safer around those they consider similar, even if it's something as silly as similar skincolor.)