There's certainly an element of luck.
I think you're stretching this argument a bit. There's plenty of cases where key players of teams were drafted in mid to late rounds and contributed heavily. Even some undrafted FAs.
If the draft was truly as important as you wrote, the NYJ, NYG, CLE, & the Raiders would be constantly in the playoffs ( well maybe not CLE & the Raiders, they sued the NFL and won, therefore they are frowned upon by Goodell).