There's no more excuse for them as they have the big 3 now.
Durant
Irving
Simmons.
This big 3 is strong enough to bring this team into the championship, the only problem is their chemistry and the two superstars passion to play as they have asked to be traded, hopefully that will not affect their performance in the season to come.
The Nets have the big trio only on paper. So it seems to me the Nets' chances of reaching the finals next season will probably be close to zero because, as you said, they might have some problems with team chemistry. Moreover, Durant and Irving are the kind of players who care more about individual achievement than team results, while Simmons looks like he has no motivation at all.
Let's compare him to Klay Thompson because both players missed a lot of games for one reason or another. As I see it, the big difference between these two players is that Thompson had a lot of enthusiasm and desire to get back on the court as soon as possible, and we could notice that in his interviews. At the same time, Simmons doesn't seem to have any enthusiasm about coming back at all.
So I'd say the Nets have "the big duo and a half" now, not the big trio.