Pug
In it's heyday Sheffield City had a grand total of four "Puddle Jumper" operators, KLM pulled out, apparently, over aircraft performance, Sabena pulled out due to poor loads, BA dropped the LCY route due to poor loads also and, these days, Aer Arran have enough problems of their own without concerning themselves of any Sheffield petition.
As you've kind of admitted yourself any protest/petition to reopen the STOLPort is a case of "banging head" and "brick wall", the stats speak for themselves, of the previous four puddle jumper operators at least 50% lost money on the operation whilst the remaining 50% remain questionable regarding the same.
So where is any new airport operator likely to find the likes of an ATR42 and/or geriatric DHC8 operator to come and offer scheduled services ... Ah yes, there was Air SouthWest, ah yes, there was Air Wales, Air Wales in particular tried some niche routes and it caused them to close down, perhaps they could have added Sheffield to their route network and closed down even sooner!
OK, there's, perhaps, Eastern with their Jetstreams but having seen the "regional" fares they like to charge I can't really see anything taking off and anytime soon.
Time to switch off any life support system for Sheffield City Airport perhaps!