There's a lot of back and forth in this thread about deadlifts "being the devil", so I'm glad you brought up flexibility. ROM gets more important the older you get. If you're a washed-up meathead (like myself) working on flexibility makes it easier to get out of the bed in the morning and some mornings it makes it _possible_ to get out of bed.

Doing yoga (yeah, I know) has fixed my hip flexor issues and got my lower body lifts to near PR levels again.