Tristan Thompson is definitely not a bad player. He's been pretty good as a defender, rebounder, and has been getting better as a shooter to become a regular double-double guy. Dion Waiters definitely didn't work out as a big scorer next to Kyrie Irving, but he's been a big force as a leader on the second team that essentially plays as a starter without actually starting.
The biggest issue this season has been the constant changes to the
starting lineup by Mike Brown so that only Tristan Thompson and Kyrie Irving were consistent starters. Alonzo Gee and Earl Clark evenly split time as starters before Luol Deng arrived to provide some stability there. C.J. Miles is the starting SG, but plays more like a 6th man that can hit 3 point daggers. Anderson Varejao had the starting center job until the Andrew Bynum phoenix rise began and fizzled out, so at least he got back what he should've had all along. The minutes played shows a lot of the issue as there are only three players playing 30 minutes or more (Varejao, Irving, and Thompson before Luol Deng arrived) and the rest play 20 minutes or so to make them appear to be a team of sixth men. They've been lucky to not have any major injuries, so there's no reason for there to that much turnover in the rotation other than players that don't fit or belong there.
They need to sort out the SF and SG positions because Luol Deng has Earl Clark, Alonzo Gee, and Anthony Bennett behind him and nobody at SG seems to want to step up to play as a legit starting SG. Luol Deng was out last night, but Jarrett Jack started in his spot, which says a lot about their confidence in either Clark or Gee, so one or maybe even both needs to go. Just looking at his recent performances, Anthony Bennett's playing better and more consistently when he's gotten 20+ minutes lately than just sitting on the bench and coming off for a few minutes when Brown doesn't know what else to do.
Beyond just the way the lineup's been handled, Mike Brown's responsible for the way the team loses big leads after the half or starts poorly to put themselves in a hole right away. The 2nd team this year is much better than the one they've had in previous years since it's not filled with undrafted players that they were forced to play because they had nobody else of merit, but it sort of merges with the 1st team into a mess where it's hard to tell when they've got a full set of #1 players and when they don't. They've got the talent to be in the playoff hunt if they can figure out who the dead weight is that no longer needs to be there.