Everyone but Randle is a potentially ending contract tradeabe in January.
Those trades, which will happen, may bring back multiple second rounders.
But Clippers used cap space the Knicks easily could have had to obtain Moe Harkless and a first rounder. I'd take that over Payton + Ellington.
Grizzlies used a trade exemption to obtain Iguodala plus a very intriguing Golden State first rounder. I'd definitely take that over Bobby Portis.
Suns had used their cap space to acquire Aron Baynes and a first rounder. Can't blame the Knicks on this one, they were for holding out for two max free agents at the time this deal was consummated, but it's another "coulda been". Similarly, taking TJ Warren would have come with the 32nd pick overall (which itself was flipped for three second rounders, but could have been, say, Bol Bol).
So the Knicks, effectively, could have signed Randle and Bullock and done the above and still saved their room exception:
DSJ/Ntilikina/Kadeem
RJ/Bullock/Trier
Iguodala/Harkless/TJ Warren/Brazdeikas
Randle/Knox
Mitch/Baynes/Bol
Plus extra 1sts from Golden State, Philadelphia, Miami. And you tell Iguodala "Play hard for us, give us a list of five teams and we'll trade you there in January", meaning you might extract value for Iguodala. Or, worst case, you waive him in February. You try to move TJ Warren as well throughout the season for nothing but an expiring.
That team is better on the court than what the Knicks will have if the shooting can be sorted out, plus better positioned in the long term.
Even hitting on one of the above trades would have been nice. Instead we signed a lot of kinda valuable 8th men. Unimaginative way to build a team.