The entire generation was a cluster fuck.
Selling nearly half as many consoles as the generation before is not “not bad”. Especially when launch window sales weren’t really that bad at all. The gap got wider and wider as the generation progressed. They’re 10-15 million units behind a console that released 3 years ago.
Xbox spent the majority of the generation tinkering with hardware instead of bringing games. This is the root of all of their problems. It’s not yet fixed. We still have promises of jam tomorrow.
Selling 50 million consoles with "no games" (as some members of the forum like to put it) is not bad. I think the 360 gen was an outlier that was caused by PS3 releasing a year later.