I think you are missing the point. Our first 11 could compete with any team at its peak. But we didn’t have a deep squad. Whatever you think of players such as Ozil, Sanchez, Pogba, Lukaku etc, they were far more accomplished players than Eriksen, Alli and Dembele. Poch made the team better than the sum of its parts. So Kane was better than lukaku but imagine being able to call on Martial or Sanchez to support or swap with Lukaku. Mata to support Pogba. Chelsea would have similar squad options. More than Poch could call on and crucial in one off games where margins are small.
These teams were not as consistent as Spurs over the season but were more than good enough to beat us in one off games. It certainly wasn’t the case that we clearly had the better squad and were outright favourites when we played them.
So if we look at when we did get through the semis, we then played Chelsea in the final of the carabao cup, with a midfield pivot of Bentaleb and Mason, against a team that went on to finish as Champions. We played Liverpool in the Champions league final we had a midfield pivot of winks and Sissoko. In neither of those games were we favourites and us winning would have been an upset.
We didn’t lose the games because of bottle. We lost because in the end we didn’t have the squad depth or variety to change things at crucial moments in the game.
With regard to Harry, Our squad was as good if not better in his last season than Poch had at his disposal imho. Harry knew how to build a beautifully balanced squad. We had world class players like Van dear vaart, Modric and Bale, and King at the back with talented strikers in Defoe and Adebayor. Sadly as brilliant as he was at building the squad I don’t think he was as good as Poch at using them game by game. I do think that squad could have done better than 4-5-4.