Man U only started showing good results at the end of the season... But failed to achieve anything other than a place in the Champions League next season... It's probably too early to talk about any success because Man U has always been a top club that has often played in European Cups... This season they haven't won a single trophy, although they have competed in many competitions... I think they have a lot of work to do...
I would say given the pit they were in last season, it's tremendous achievement for them to make into top 4 at least. They have gone through a lot over the years so they did well. Also you can't expect them to get hands on everything in just a season of rebuilding. It would take a bit more time before they really can be considered as a contender in competitions. This season they actually won EFL when they faced Newcastle in the finals and scored 2 goals.
I would however agree that they still need to work a lot and hopefully ten Haag will cover that in next season.
The progress made by Erik Ten Hag this season is quite good even though it's only the EFL trophy. I think it's still appropriate to say that the team is growing under the tutelage of Erik Ten Hag, now they have improved the team very well and this is a pretty good job while their career is still in one season.
I believe that in terms of time and process, Erik Ten Hag will definitely be able to manage Man United well and return to fierce competition, so we have to see next season how this team grows after Erik Ten Hag took over.