Interesting that you feel the midfield was 10 x better for having Ndombele instead of Sissoko. I would say that it was far more due to having Ndombele instead of Dier that made the difference here. I say this because the player who was playing in the exact same position that Dier has been playing was actually able to receive the ball from his defence and get it forwards with good movement, dribbling, decent mobility and effective passing, four things which are completely alien to Eric Dier's game.
In the first half I agree that Eriksen did tend to play a bit too conservatively, akin to the way that Harry Winks plays. It was a 5 or 6 out of 10 type performance (again - akin to a typical Harry Winks game). It was the second half where Eriksen started to grab the game by the balls and became our main creative force, getting on the ball constantly and playing good passes in the opposition's last third of the pitch. I have yet to see Winks perform that way for Spurs (perhaps because he hasn't been played enough in a midfield position that allows him to do this?) Eriksen may not have been amazing but he was still probably the best player on the pitch and certainly Spurs' best player.
Lo Celso looks to be a decent footballer, although he does seem to want too much time on the ball. However I am starting to become a bit concerned as to what Lo Celso's role will be in Mourinho's favoured 4-2-3-1. I'm not sure that he is one of the deeper two midfield players and doesn't look to have enough pace to play as either of the wide two of the three. It therefore seems he is competing with Dele to play as the free player in the centre of the three and it looks as though Mourinho likes that player to be playing quite high up the pitch close to Kane, is Lo Celso physical enough to play that role in the PL? I can't help but think that he was bought by Poch specifically to play in his favoured diamond formation and might be a bit of a square peg for Mourinho's system