The rise in popularity of "functional fitness" and its accompanying ideas about mobility and flexibility have made it seem like everyone should be a contortioni

The rise in popularity of "functional fitness" and its accompanying ideas about mobility and flexibility have made it seem like everyone should be a contortionist, but if you're only an amateur athlete, the mobility you should focus on is just what's necessary for your sport. Like the paragraph you cited says, extra flexibility is sometimes a bad thing. Weighted mobility, once you can achieve the positions you need to, is a better progression than trying to increase ROM.