That's fair enough, you have faith in his abilities. I don't really understand how you can have faith in the abilities of a manager that hasn't shown any promising sign in two seasons and a manager that also has no actual good track record at the highest level.
And yes people, including myself were excited about his potential but it's important to emphasize on the fact that it was only potential, ETH isn't a proven winner at the highest leve. He is a proven winner as Ajax's manager in the Eredivisie, his European resume with Ajax isn't impressive at all beside the 18/19 campaign. So in my opnion people should logically use hindsight and reevaluate their enthusiasm instead of clinging on a previous uneducated position.
And it's not something specific to ETH and United, the same was true for Rose, De Boer, Villas Boas, Lopetegui, Gasperini and many other managers over the years because most managers with potential will fail to match higher expectations which is perfectly normal, not everyone is meant to be an elite manager.