Despite there being a lot of floating debris left after the Titanic disappeared underwater the victims never had a chance as they were soaked in near-freezing water that would have killed them, even if they could avoid other panicking people and remain composed and focused enough to attempt finding and lashing pieces of debris together and getting out of the water.
While the majority of the death certificates issued stated the cause of death as drowning, the vast majority in fact died from hypothermia. Let’s be clear, they “did.” Specifically, when (untrained) people unintentionally go overboard or fall into water, one of the first things they reactively do (often in a panic) is try to grab anything around them to keep themselves afloat. But more importantly, unlike how the movie portrayed it, the act of using floating debris to survive is far more complicated than it sounds. For example, even if a chair floats, you can’t exactly just sit or stand on it while it’s in the water - unless you have incredible knowledge of ocean physics and balancing strength.
People indeed used the debris to try to keep themselves afloat. Sudden immersion into freezing water typically causes death within minutes, either from cardiac arrest, uncontrollable breathing of water, or cold incapacitation; almost all of those in the water died of cardiac arrest or other bodily reactions to freezing water within 15–30 minutes.
The main problem all of the passengers faced when abandoning ship was extreme cold, not drowning. As for trying to put together a makeshift raft, few probably had the skills to do so. Even if they did, with panic and chaos all around, being denied access to the lifeboats, and the ship sinking right underneath of them, most were likely not in a state of mind where they would be able to put together a makeshift raft out of furniture or other items.