You go on to make some interesting points, but I feel I'd have to defend Abellio here - they did run the Northern franchise for a dozen years (a fleet of hundreds of trains, serving over five hundred stations - from the bleak rural stations like Dent to the commuter lines into cities like Manchester/ Leeds).
Northern is probably the closest TOC to ScotRail that we have in terms of complexity/ geographical area/ diverse markets (Northern is actually bigger than ScotRail in terms of fleet size and stations served, with additional complications caused by significantly more interaction with other TOCs and the UNharmonized conditions that staff were on, having come from First North Western/ Arriva Trains Northern).
There are things to criticise Abellio for, sure, but if they can run Northern for over a decade then I don't think it's fair to say that they'd have no appreciation of managing a diverse TOC.