Jesus, I can't kept up with the goalpost moving. From new "worst contract in the league" to "well, I, uh, am just not a fan of overpriced swan songs."
1) All of the guys that you just mentioned were physically toast when they signed their last contracts. At best, clearly diminished. At worst, they were practically bed-ridden like Dirk. And only Timmy was on a team with any realistic title hopes at the end.
If Steph only took a $20M extension, does that realistically put them in position to compete for a title? $40M less to Steph doesn't mean that they have $40M more to go spend on players...that's not how the cap works.
2) All but Dirk and Tim played for other teams. Most of them came back to their original teams strictly for the sentimental value of retiring with them. How important do you wager it is for Golden State that Steph never plays in another jersey?
3) You're assuming that the 26-27 season will be Steph's last. He was All-NBA last season and was the toast of the Olympics two weeks ago, where, by the way, another 40 year old was very clearly the best player on the team. Until he shows clear signs of diminished play, accepting $20M/year is absurd.