There is no one to blame here and indeed luck was on Manchester United's side so they were able to win the match in the final minutes, I think the substitutions made by Klopp did not affect the team's performance in that match and in my opinion Liverpool's defeat was due to their bad luck and On the other hand, the Manchester United team played a little better even though they were not favorites in this match, but they managed to answer these doubts quite well.
This is a trophy that is possible for Manchester United to win this season, they are very close to the FA final this season because in the semifinals Man United will not meet a tough opponent.
I agree with you that nobody is to be blame but though most persons are feeling that the bad performance of Liverpool was as a result of the changes Klopp made, so for me I think that's far from the reason why Liverpool performance was not that consistent and besides we know how Klopp pattern has been working for the club which has lead to there numerous wining and being on the position they are now, however one thing we most also no is that after a coach has established his pattern to the players to use, it will be left for the players to effect the strategy in other to win the match, so in terms of Liverpool on that match they failed to utilize it because Manchester United did not really give them the opportunity to and it got to a point where most Liverpool player was no longer confident on themselves that's why on the first half they barely hold a ball without being intercepted by the Manchester United players.
Man United, playing at home, is very confident and when they know there is an opportunity, they have a big chance of controlling the game. Liverpool didn't play badly but were at a disadvantage, their performance was just normal especially since both of them had a big target to advance to the semifinals. I admit that Man United performance at that time was quite good. The players mentality rose in the final minutes. So basically there is nothing that can really be used as a benchmark, Man United is clearly unlikely to get the EPL trophy this season because they are quite far apart from other clubs. Their opportunity now is the FA Cup and it is no wonder why Erik Ten Hag insists on getting 3 points in this match.
Don't forget that the Man United versus Liverpool match also applies to Man City who will play Chelsea. In fact, I suspect that Chelsea will appear more aggressive, in the EPL they have no chance, so Chelsea can only fight for the FA Cup this season. Man City must be careful because every time they meet Chelsea their game becomes unbalanced.