1.) You're comparing 2 completely different champions in 2 completely different roles in 2 completely different lanes. Comparing both of those champion's stats is fucking useless because metas will affect both lanes/roles differently.
example: Darius, just like any other juggernaut, requires a specific set up/scenario for him to pop off. There for it is easier to keep him in check compared to someone as slippery as Ahri who also has a pretty significant CC ability.
2.) Just because Darius is a "simple" doesn't mean he automatically deserves a higher win-rate/pick-rate. The meta decides that.
3.) I'm assuming you are a Darius main. If you like the champion, why are you basing his effectiveness on how much OTHER people play him? Darius can do just fine if you aren't a half brained monkey. If you're struggling with him, trying improving your own gameplay first