I’ll comment more about Monty when I get back to a proper keyboard, but if your logic were to apply to all such events, we would need to tear down all Vietnam memorials and try to forget that ever happened. Do you think that a good idea too?
They are honoring the sacrifice of those who fought (and often enough died) trying to liberate them. The bad plan and planner has no bearing on their valor or courage. There were plenty enough examples in Market Garden when the plan was falling apart and Allied troops decided to surrender or self-sacrifice rather than let Dutch civilians be incidentally slaughtered by German troops. Worth remembering and holding up to future generations as how one should act.
Also pretty sure Monty isn’t going to be even mentioned much there. He was at one point a very good general but then started believing his press.
Americans don’t consider Vietnam to be a success. Montgomery considered Market-Garden to be one. No one is taking it out on the troops who did their duty during the week of the 17th. of September of 1944. That wasn’t the case with American veterans of Vietnam.
Memorials are different than reenactments. I don’t think anyone thinks reenacting Vietnam is a good idea.