A great manager like Ancelotti has also experienced ups and downs in his managerial career, so I don't think we should judge Ten Hag too much because of his poor track record with Manchester United. In the Bundesliga with Leverkusen, Ten Hag might be able to achieve a lot of success, like he did with Ajax. However, all judgments come back to each person perception, we can refer to the case of Kompany when he first came to replace Tuchel, I remember many people also underestimated his ability.
We do not know what will happen to Leverkusen for next season with Ten Hag, but the negative view of Ten Hag is, of course because of his track record with United. Maybe it is true, the main problem may not be with Ten Hag, because in fact, with Amorim at this time United is also slumping.
Ten Hag gets trust, and this should be a good moment for him to get praise. he should get some valuable experience while he is handling United.