A series of names of coaches after Sir Alex Ferguson can indeed be considered to have failed in achieving the desired targets. For me, when the shadow of the past story is always a benchmark, then it is burdensome for the coach's psychology.
Ruben Amorim could be one of the coaches who will be challenged to reap success at Old Trafford, I hope so, but I doubt it and it is likely that his fate will be the same if the past story continues to be used as a target. It's okay, but it has to be realistic.
So in essence, lowering expectations for Manchester United is good advice for all fans. They don't need to expect much from the new coach and the existing squad, but they just need to hope that one day this team will compete again when the squad is really better than the current top 3 teams.