You'd still have to go to the station regardless (collect from a TVM via a ToD) or to the ticket office, so it doesn't take twice as long. For people who already didn't have a local station with a regularly staffed ticket office, going online was a major plus since it went live just a few years ago. Is a bit clunky though.
It absolutely does in some situations: for instance buying a ticket for one leg of a journey through a London terminal where you need to interchange. You have to go out of your way to look for a TVM (and hope there aren’t queues). It completely defeats the object of buying online: why can’t all tickets just be downloaded to your phone?
The site is indeed very clunky and it often takes several attempts to complete the transaction. Overall it’s disappointing as technology is supposed to improve things whereas objectively speaking this doesn’t, and it’s often more convenient to buy at the local ticket office (accepting some don’t have those).
The horrible thing is that the RMT will now punish punters even more for something that they will not and can not "win" on.
But you say that about every aspect of the wider dispute, seemingly with no acknowledgement that the government’s unnecessarily belligerent approach has directly caused much of the disruption: newsflash, they aren’t on the side of punters either…