The ultras thing works if every single person is 'on-board' with it.
I personally do not fall into that camp which is why after a few occasions I tended to avoid being in the same stand as the displays if possible. That way I had no bearing on them and reduced the chance of any conflict etc.
I still think the all seater stadium is the main atmosphere killer as the most atmospheric Dons games I've been to have been when everyone has stood the entire match. Raith Rovers in the cup back in the Dingus era sticks in my mind for the sheer anger that rippled through the stand.
In my experience the only true 'Standing' Stands in the league are 'the Shed, Parkhead Away End, and the Roseburn (unless the full stand has been allocated).
Everywhere else either has over zealous stewards/ cops or you find the person behind you insists on sitting resulting in arguments. The latter happens all too often at Pittodrie and stupidly it happens in the South Stand which actually requires you to stand up if you want to see most of the pitch. (Typical of a cheap conversion of a former terrace). I recall a fight almost breaking out in a sparsely occupied RDU when an elderly gentleman started on a couple of teenagers who were stood up infront of him. There were hundreds of empty seats around but neither party was prepared to move and the stewards/ cops ended up having to get involved.
At the QOTS Hampden semi, the Glasgow Reds got into an argument with the Families sat behind us because we did a short 'flag surf' for the teams coming out. The argument continued when the entire North stand remained standing and 2 of the mothers demanded we sit down because they & their kids couldn't see, completely oblivious to the fact that even if we did sit down the row in front would also block their view. As I recall the argument only stopped when QOTS scored their 2nd and the atmosphere in the stand began turning ugly (I think one of us may have said something not very gentlemanly).
A 'family' atmosphere is not a 'football' atmosphere and personally I think those families should have had more sense than to buy tickets in the North Stand. If you have small kids and there is a family section then that's where you should go etc etc.
Sitting down is for relaxing, quiet contemplation, or for all too many people, working. Standing tends to mean you are alert (takes longer to develop frostbite/ hypothermia), more open to interaction/ conversation and/or a bit of a sing song. Standing also allows you to move to get a better view or away from 'undesirables'
Same for concerts. If I find out a gig is all seated it has to be someone quite special to me to buy tickets.