This may be way off, but maybe our ex-players don't want to throw Ole under the bus because they only remember him as a player, and don't really know him as a coach.
When you've been in the most high-performance dressing room in football with a guy, with elite mentality being the norm, and won everything together, it must be hard to think that same ex-teammate could let standards slip this far as a manager. "I remember how hard he worked in training. I remember how high his standards were. How cutting he could be with his comments when we weren't playing well. Surely he's laying into these players."
Love them all, but what qualifies these ex-players to comment on what's required of a manager, apart from the generic 'attitude' and 'standards', etc.?
Rio can definitely pinpoint all the glaring issues with our defence. Scholesy can spot the issues in our midfield.
But they're looking at symptoms, not the cause.
Sir Alex built an entire system of running a football club from the ground up that led to that dominant period in our history. These ex-players were just cogs in that machine, so they only have their own limited ideas about what it was that made them successful.
Sir Alex was unique in the sense that he was the designer of the system as well as the orchestrator, for decades. That is too big a job for one man nowadays.
Which is a long way to say, yes, Ole is very limited as a manager and not the right man for the job, but until we have a new system in place with a DoF that is ready to compete in the modern football world, no manager alone is going to change things at this club.