I see your point and it is a good one. You do need 2 ball handlers with the ability to facilitate.Lots of really good, thoughtful responses that were a pleasure to read. Thank you all guys for that. I want to clarify few things. Of course, Lauri is helping the Jazz right now : he is a very good player. I was talking more about turning the Jazz into a contender and that is why I looked at rosters of the current contenders. Almost all of them have two offensive forces that can also be playmakers. Sometimes you can get away with your second option not being a great playmaker but then they have to be an awesome defender like AD. Lauri is none of that: all he brings is scoring.
He IS similar in that to KAT, Porzingis and (a bit less but still) Thompson. And all of these players could not cut it as a legit second option on a contender: the teams needed to have a third all-star to cover their deficiencies by bringing playmaking or defense. Lauri is a poor second option, but he is an awesome third option. When you have two stars who are both scorers and playmakers you can start filling out the roster with role players (that what Dallas is doing right now). When you have someone like Lauri, Porzingis or KAT you still need to find another star to become a contender.
Building around Lauri simply requires adding two more star pieces instead of one and this would be very difficult to pull out even for Ainge. Instead of one successful trade you will need two, or scoring big in both trades and drafting.
However they dont need to be you #1 and #2. They can very well be #1 and #3. And either Sexton or Keyonte could very well be/become that #3 (or #2).
Just for reference... the guy Lauri gets compared to most often (Dirk) averaged 2.6 assists in their championship year and 2.4 as career average (career high being 3.5).
So again. I dont think the bar is 5+ for him. And I'm pretty sure if he finds a great partner to run effective 2 man game with he will increase his assists easily. After all, from Jamal Murrays 384 total assists this season 151 have gone to Jokic.