I understand what you're saying; positivity on the way out can ensure that you don't burn bridges as nobody likes being told that they're doing a bad job.
But this isn't the right thing to do.
Show some care for your colleagues.
If you're leaving them in the same position or worse off, then it's your responsibility to say: "I'm going now and I've enjoyed my time here for the most part, but I really hope that you can try and fix some of these things x, y, z for my colleagues Simon, Jack and Andy."
Avoid being rude or selfish.
Reframe the conversation so it's about helping your colleagues out and not negative feelings.
Be positive, caring and constructive at the same time.
But this isn't the right thing to do.
Show some care for your colleagues.
If you're leaving them in the same position or worse off, then it's your responsibility to say: "I'm going now and I've enjoyed my time here for the most part, but I really hope that you can try and fix some of these things x, y, z for my colleagues Simon, Jack and Andy."
Avoid being rude or selfish.
Reframe the conversation so it's about helping your colleagues out and not negative feelings.
Be positive, caring and constructive at the same time.