I was watching a programme last night with Susan Calman about cruising in Antarctica (not proud of that but there was nothing else on!) and she went on a little sub. It showed what a real submersible SHOULD look like.
I was struck by how ridiculously bare Oceangate's Titan interior was at the time, with little or no secondary systems. - Compare that with the safety video from these guys, who admittedly don't go as deep but the focus on safety is way more apparent.