I definitely agree that Ole Gunnar Solskjaer did not really make a great job during his stay at Manchester United and the club also acted pretty weirdly in my opinion. He had such bad statistics for a club like Manchester United but still they kept him as a coach for a few more months and the end result is that Manchester United did not reach the Champions League.
To be fair though i am not so sure if an other coach would have way better results with this team. It is just not the same Manchester United as it was a few years ago or so. Clubs like Manchester City and Liverpool completely overtook ManU in the last years. Of course the transfer of Ronaldo does not really help if you want to build a strong and young team for the future.