The standard argument against this says that while every bug, security breach and inconvenience that arises due to the alternative (non-standardised, proprietar

The standard argument against this says that while every bug, security breach and inconvenience that arises due to the alternative (non-standardised, proprietary DRM, or no in-browser DRM at all) may individually make engineers thinking about the system from an engineering standpoint break out in hives, the discomfort will also be felt by end users and associated with DRM, therefore serving as an obstacle to its public acceptance and proliferation. As a relevant comparison, I think the current situation with the plethora of proprietary video game DRM solutions that are universally recognised to be terrible is strictly preferable to an alternative world in which video game DRM Just Works™, possibly with hardware support: in no small part thanks to it, we have a healthy amount of pressure on game studios to hold back and a market for DRM-free publishers such as GOG, and perhaps more controversially a healthy piracy ecosystem to punish the worst actors in the market.