I can't see anything in your comment that highlights how the Glazer ownership is distinctive from the Martin Edwards era. Why wasn't Old Trafford modernised prior to their takeover in 2005? What grand strategy lay behind responding to Arsenal invincibles and Jose's Chelsea cantering to league titles by signing Djemba Djemba (as Roy Keane's replacement!), Liam Miller, Alan Smith (the new Cantona apparently!) and Kleberson!
The club has long been a profit-maximising machine whose archaic set up was masked by Fergie's phenomenal management. Up until 2013 and 8 years after the Glazers too over, Utd were still successful on the pitch and there wasn't this fevered talk of Glazer's lack of "strategy" and "leadership." What changed in 2013, Fergie was gone and the common denominator behind the club's success was gone.
The Glazer's key error was seeking to replicate what worked under Fergie - appointing a "good" manager and trusting him, largely, with the player signings. As each manager proved unworthy, each successive new manager was faced with a squad of players that needed a clearout.
As for missing key signings, do you think we didn't miss out on key signings in the Edwards's era? Remember Alan Shearer in the 1990s, Zidane was also supposed to join us from Bordeaux in 1996. I remember feeling frustrated when we missed out on the South African captain, Mark Fish. In 2003, Harry Kewell left Leeds for Liverpool suggesting that United were going nowhere and he could win more trophies with Liverpool.
I think most are emoting about our present abject lack of footballing success and scrambling around for easy answers to which the Glazers present archetypal villains. We need to be clear exactly what and when things went wrong.
No one with enough financing to take over from the Glazers would do anything other than try and make a profit from their investment after making the hefty outlay to purchase the club. Utd is too big to be a City, Newcastle or Chelsea. So we can pretty much forget about having a benevolent owner who simply wants to see us win trophies. If it's about putting more investment in infrastructure, appointing a competent DOF (moving away from the Fergie era of the all powerful manager), and setting up a good scouting system, I am not sure you necessarily need a change of ownership to do all of that.