No matter how you shake it, Radke accumulated 45 rWAR in 11 seasons. He posted 5 rWAR seasons two times and 6 rWAR seasons two more times.
Radke was better than you're giving him credit for being. Whether he got there through what we consider the "optimal route" is irrelevant, as he was consistently way above average as a starting pitcher. Advanced metrics are only useful in smaller sample sizes, when you reach several thousand career IP and a guy is a very good pitcher using standard stats like ERA+, he's a very good pitcher, period.
If Joe Ryan has an 11 year career averaging about 4 rWAR per season, that's a 99th percentile outcome for him.
As for the leaderboard, go grab a random team and place Radke on their pitching leaderboard. He's top five in most orgs and top two in many others. For example, he'd be fourth on the Phillies, third on the Cubs, fourth on the Red Sox, second on the Mets, first on the Brewers, etc.... People really undervalue how bloody hard it is for a pitcher to accumulate over 40 career WAR.