I mean, no... The pick looks worse with every passing year.
If we had passed on Paul Pierce in 1998 for some JAG who would go on to bounce around NBA benches for his career we wouldn't still be arguing we made the right pick.
This is essentially what happened when Giannis Antetokounmpo fell into the Celtic's lap, and then they passed on him for a center from Gonzaga.
Kelly has proven: 1:Injury prone. 2:To have little to no value on the trade market. 3: To have one NBA skill that he's afraid to use.
He is exactly the kind of player that you could easily replace, either by trade, or with a low level free agent any given year. You should almost NEVER waste a lottery pick on a player with Kelly's ceiling. It's so much better to pick a player like Giannis in the lottery even if he fails 2/3rds of the time in the NBA because those high ceiling players - when they develop - have a huge monopoly on trade value. How many Kelly Olynyk's is Giannis currently worth? 3?... 5?... 10? I don't think any number of players of Kelly's caliber could currently net you Giannis in a trade.
Additionally, You can't simultaneously think Kelly was a good pick, AND be mad that the Celtics can never pull off a trade for a premier player... The reason the Celtics don't have that Demarcus Cousins, or Paul George, or Jimmy Butler, or Blake Griffin, is exactly because they have Kelly Olynyk to offer in a trade instead of Giannis...