The thing is, when building vessels that are going beyond the normal range, then you use materials in innovative ways. Carbon fibre might not have been meant to withstand pressures that deep, but then again neither is anything else
It can, has, and will again be successfully used at that depth and deeper. Also remember that it's not just the materials, it's how they are put together
We don't know that none of the resurfacing methods worked - no-one knows right now where the vessel is - it could be bobbing along at the surface, but with broken comms
There were various layers of emergency plans, but that reduces risk. It does not eliminate it (true for many activities). The risks were made very clear to those intending to make the dive - rather like astronauts know there are risks despite many mitigations and emergency plans.
GPS only works at surface and the satcomms to a few hundred metres. That doesn't mean a failure to provide proper kit, it's that things stop working at depth, and that's why they rely on pings at depth, then communicate by message when nearer the surface to establish location for retrieval.
Also, I think being classed isn't really applicable here. There aren't agreed standards because there are so few vessels that can go that deep. Making sure vessels reach safety standards is important when there are standards to be met. But it's not the right administrative process for innovative vehicles