You are truly hilarious.
First a list of 10-15 guys from a time span of nearly three decades, with a lot of those guys being little more than "just another guy" type players. 30 years, you came up with 15 guys to make your point. Out of the whole league. And you had to include some drafted players just to get to your number of examples.
Also, one of the drafted guys actually reached his full potential because Danny traded for him after Danny was really high on him when he was drafted. Danny kept an eye on him and got him dirt cheap
I think it's pretty clear that some GMs found a needle in a haystack, which is what finding that really good undrafted player really is.
And my word. Let me quote this so as not to misquote you.
I’m an Ainge guy but both of those signings were one of his biggest mistakes as a GM.
His biggest mistakes as a GM was having Tacko and Waters on two way contracts for 2 years? Really?
Not trading away Perk.
Not failing to bring back James Posey
Not drafting Olynyk after he personally scouted Giannis.
Not trading for Kyrie.
Not signing Kemba.
Not the handling of Ray Allen in those last couple years.
Not constantly giving his coach bad benches filled with youth
Not signing and trading Hayward to Indiana.
You're going to go with Tacko and Waters, 2 two-way players that didn't develop as one of his biggest mistakes.
Wow.