Watched a video not long back on why about half of Premier League transfers fail. Part of the reasoning was this: say you evaluate a player in six characteristics (positioning, passing, stuff like that), and you're 90% confident in their quality in each characteristics being up to scratch. What's the probability the the player will be good enough? Some people have an instinct to say 90%, but in reality it's 53% because the probabilities stack (0.9x0.9x0.9x0.9x0.9x0.9 = 0.53).
Point is, you can look at players in other leagues, try to evaluate them, but however you try to judge them you'll only ever be so confident. It's not just us, this is just what happens when you're gambling on players from the Scandi leagues on our kind of budget. There's been an awful lot of more expensive flops than we've signed. We've gone the route of not signing any proven quality at this level and this is the risk.