I would say 90% of the time, there is a failure in design. Most of the time the designer does not fully understand the problem because the product hasn't been

I would say 90% of the time, there is a failure in design. Most of the time the designer does not fully understand the problem because the product hasn't been tested yet. Additionally even after the product has been rewritten 90% of the time the new design is wrong. Often the second design is slightly better or worse than the first design because the second design is also a shot in the dark. Why? This is because there is no way to theoretically prove a design is the correct solution to the problem. The only way to prove a design is to test it. There is no science or proof behind "design" only "design principles" and anecdotes... all of which can be broken and tend to evolve over time. This is why designers tend to be artists rather than scientists. Designers are hired for problem spaces where no theoretical solution exist. If most designs are wrong how do products even exist? Well computers are fast enough to cover up design flaws. Hacks can be made to bridge gaps in designs. Overall designs are wrong but can be patched to make anything work.