What matters is the capacity per volume, per mass and per dollar.
The capacities per volume and per mass for these glass slabs are already very competitive. They are about the same as for the best tape cartridges currently available. The capacity per volume is about twice better than for the best HDDs, and the capacity per mass is much better than that, because HDDs are very heavy.
If such optical storage had not been so expensive as it is for now, it would have already been much better than any cloud storage. The slow writing speed is similar to that of file downloading or uploading over the Internet. Reading can be done much faster than writing, because it uses ordinary lasers and a video camera, not the very expensive femtosecond-pulse lasers used for writing.
