100% this.
Being an away football fan is one of the few "entertainment" industries where you more often than not pay money for a ticket, and then get sent a random Block/Row/Seat which you have had no input in. You get into ground, decide you don't like the seat you have been randomly allocated, so move elsewhere and it inevitably leads to issues. Often because some people get very particular about the seat they were randomly allocated.
Credit to Wigan, whose tickets were labelled with unallocated seating. Shame never got to use them!
I know York City have had issues in their new stadium, as they've classed the stand behind the goal as "unallocated seating", however, the new ticketing system cannot function with this and has to print a seat number on the ticket. Therefore you then get regulars who know it is unallocated seating, sitting in the printed ticket seat of someone who is not a regular or a visitor to the stadium.
Derby (amongst others) often keep a number of away tickets back as a "singing section" and you request to be allocated into that area when you are purchasing - both online or phone/in-person. So it must be doable, but perhaps requires a bit of logistical organisation and extra admin.
Equally, I have noticed some clubs this season, selling tickets for their own away end on their own website, enabling individual seats to be picked by visiting away fans when they purchase. Other clubs have claimed they can't officially make things unallocated seating due to their own safety certificates, i find this hard to believe.
Has to be a solution somewhere, the easiest one being unallocated seating with guidance given around which areas might suffice to your particular need e.g. if you are unable to stand for prolonged periods, then perhaps head to the front half of the stand or to the side.