They’re a very loose contender. Most lineups are going to feature two or three bad defenders. Not below average, but bad, in Kyrie, Harris, Curry, and Mills. On top of that, injuries are going to be a major concern, both throughout the regular season and postseason. Kevin Durant played 55 games last year, and that was the most of anyone in that proposed starting lineup. (Yes, Kyrie’s absences were somewhat self-inflicted, but he’s played more than 60 games once in the last 5 seasons, so the point remains).
So yeah, while we always caveat “if a team can stay healthy”, it’s a much more relevant caveat with the Nets, and it extends to their bench, with a key reserve in TJ Warren having not played in two years. They can score points, a lot of them, and perhaps that could be enough, especially if they also have a miraculous season in terms of health. But between the high potential for simultaneous unavailability for several key players and the significant defensive shortcomings up and down their rotation, I don’t think they’re in the top 10 of potential contenders.