I understand the Process.
OT Sam Hinkie
But if you look at the chart in that post, you see the expected value of top 5 picks. It's massively higher than any other place. You want to get more whacks, but specifically whacks in the top 5. The Celtics need marginal improvement upon already elite players, not just solid rotation players.
NBA Draft Analysis -- Expected value of a pick
A top 5 pick gives you a 60% chance at a star.
Of the 5 first round picks they have the next couple years, 2 of them have a chance to be in the top 5. My suggestion was to trade 1 of those potentials (and remember none are guaranteed to land there, just look at the Brooklyn pick which will likely be #8) plus a couple weaker firsts for a guaranteed top 5 this year. As it is, pick #30 for the next couple years for the Celtics will give a 5%/10% chance of star/solid rotation piece, which will be their own pick range for the forseeable future. Almost worthless.
As an aside, it's way too early to say Fultz/Lonzo are busts. You did add a qualifier about so far, but these guys are so young. Tatum/Mitchell are the anomalies, not those 2. Lonzo's numbers aren't that far off from Kemba's rookie year. And just look at Embiid. You can miss your rookie (and sophomore!) years and still be great.