Tottenham will surely have themselves to blame because of how they handled the game during the last 20 minutes. 2 goals up is actually a scoreline that you can defend but they failed to. PSG on the other hand deserves some credit even though initially before the game they were the favourites but fell behind and had to fight in order to make a comeback and if which they achieved.
Tottenham held the game till it got to 10 minutes before the additional 4- 5 minutes extra time before the final whistle, Tottenham coach would have instructed his players to focus more on massive attacks and defense instead of choosing to go all back to defend when they don't have a solid defense yet. PSG took the advantage to launch countless attacks on them untill they were able to get a break through which saw them come back from 0:2 to 2:2 in the game, it was a surprising comeback but PSG deserves the win.
Tottenham really tried I was even thinking that PSG would score them a lot of goals but that did not happen they were determined to win PSG and they were not even scared of PSG however just like you said they don't have a strong and good defense and they really need to work on that if they had a very good and strong defense I don't think PSG would have a chance of scoring, yes the coach would have instructed them to focus or put more pressure on attack than defense if they had put more pressure on PSG they would have scored another goal and win.
PSG did their best and they deserve the trophy however I feel that they are not as strong as before anymore they need to work on their self the coach needs to work on the team again and PSG should not underestimate anything team that they are playing any match with because I'm seeing that they underestimate teams too much that is why they are not playing like the way they where playing before.