Look at this article trying to dissect him.
https://www.cbssports.com/nba/news/should-the-warriors-consider-trading-klay-thompson-the-dilemma-of-ending-one-dynasty-to-pursue/
A need to be in Top 15 players just for the 5 year contract to be worth it?
No, I don't think so.
He had contributed a lot for the Warriors team and mostly when Steph Curry is out he is the offensive weapon.
And let us not forget how good his defense is. He worked so hard for it.
I agree that Klay Thompson is an underrated player, he is not very useful if Curry is injured, even at times when Curry will struggle, Klay Thomponson is always ready to fill the some points Curry not able to contribute.
I remember one of their classic game when they come are down 1-3 against the OKC and they come back to win the series.
check his highlights - Klay Thompson EPIC Full Game 6 Highlights vs Thunder 2016 Playoffs WCF - 41 Pts, 11 Threes, CLUTCH