Overall, the team looked pretty sharp yesterday but it just came down to a lack of clinical finishing. Tottenham had their opportunities, most notably from Son.
Over the past year or so, it's become pretty clear that he's is capable of being a world class attacker and it looks as if Poch has been more than willing to make him the centerpiece of the attack (including yesterday's final). However Son's inconsistency around the goal has cost the team recently. Yesterday, he showed moments of individual brilliance but he should have put away at least one of those opportunities. Whether or not those opportunities were created on his own or not (most were) is futile - the end result amounted to nothing.
If he can prove that he can be a more clinical finisher, I think going forward, Tottenham can build the attack around him, even more so than Kane. He's got all the intangibles (pace, quickness, dribbling, skill, ambidexterity) of being a top 10 attacker in the world - he just needs to be more reliable around the goal.