You were "the new one" here and wanted to tell people they did something that sucked terribly. Most people don't want to hear that and act accordingly.
Not easy at all.
The team member who starts to fit in and then says to the right people "It looks like our system has a memory management problem. I've got a lot of experience with this type of issue. Can I help out with designing a solution?" is far more likely to get into a constructive dialog and may move things forward.
If the OP wasn't brought in with the goal of saving a project that was in dire straits, then trying to fix what you think are the biggest problems immediately isn't going to go over well.