Still, this is the strategy with the best chances. The existing team may be too invested in the current concepts, and as a new member, if you don't speak up early, your possibilities to change something vanish with every day you say nothing.
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.