What I remember most about Havlicek was his motor, just non stop all the time. I don't recall him having the playmaking skill that Doncic has. He was a good passer, but not elite. Great defender. Not seeing him as a good comp.
Nobody likes my Ginobli comp for Doncic?
Manu is my favorite player.
When I first saw him in Kinder, my first impression was - Whoa! He is fast! He jumps like a brother! The Motor! And he has team oriented game! I was blow away. Love at first sight.
But he is a lefty and that is a special, counter intuitive trick. He scored so many of his baskets in his career that way. Luka doesn't seem to posses such go-to scoring move. I don't think he ever will and that is not a knock on him, just a stylistic thing. He might end up as productive. And that would be a 1st ballot HOF level of player.
Luka's length is another thing that separates them. Those couple of inches, paired with similar elite vision and BBIQ produce extra possibilities. More good weird angles. Fine examples would be: Magic, LBJ, Bird, Euro-Kukoč. They could all drive and dish it. And to maximize the concept: Nikola Jokić! Centers like Sabas, Ćosić (Croatias 1st HOFer) and Walton did it purely in the half court and on outlets from what I've seen.
There are many similarities though.
Their BBIQ, knowing how to set the tempo of the game. Nice stroke. Manu shoots with his legs almost glued the floor from down town. Only great dribbles can allow themselves that (Harden). I expect Luke to posses the same freedom. And that he will use that stepback more often, as he develops. Manu has is Grand-mastered. Their vision is similar. Dončić will have even more passes in his repertoire. The game is simply evolving each year.
I think both of them have that fantastic motor. All-in, all the time. Ultra competitive and they won't/didn't stop after 1st championship nor 3rd. I personally adore that trait. Manu was clearly more explosive. Both have great, long last step. Even now Ginobili, in his 40ies, can still drive (left) and dunk it. Luka...I wouldn't bet that he could.
I hope I added some value to your comparison.
Now more than 20 years later I first saw Manu, I watched a Spurs game the other day.
Guess what? Manu scores a layup. They still don't know that he is going left.