It was essentially a 1915 design copy pasted to the 1930s. With a newer model of gun, and some new engines.

What that meant was she was still hindered by the expectation of a short range brawl in the North Sea. Where stopping shells coming horizontally was the key. But even during WW1 increasing ranges meant that fire would be coming down at a very steep plunging direction.

But her double armoured deck and turtle back scheme was problematic. It meant that while certain key areas were protected, the top armor might deflect a shell into other key areas which would then be penetrated and destroyed. There was also the problem that a small volume was protected this way than peer ships. Meaning that she had less reserve buoyancy. In general German heavy ships were hard to sink by gunfire, but could be made impotent quickly. And as soon as they started to flood it was all over.

There were also serious issues with her ability to handle after a problem to a propeller or rudder that were demonstrated on her final voyage. And concerns about the placement and forget if her armour belt on the sides. And her fire control scheme, and poorly placed radar position.

And finally her armament didn't help her. While all ships in 1941 were light on AA, Bismarck's reliance on a mixed battery of single purpose guns meant she was getting less bang for her buck and thus less protection.

/u/fourthmaninaboat and /u/jschooltiger actually had a wonderful conversation on this topic in a thread last week.