To begin with, it was about loneliness - how he wrote those beautiful letters for others' but had no one in his own life with whom he could share those moments.
Then there was the over dependence on technology. It was actually very disturbing to see that the situation in the movie might not be too far off. We already see people sitting in cafes opposite each other but looking at their phones instead of talking to each other. I remember going to this gorgeous viewpoint with my friends, where you could got a magnificent view of the city. And then I did the mistake of asking them what the time was. My friend looked at the phone and never returned lol. There is a breathtaking natural view in front of you, and you are worried about the number of likes you got on your selfie. Sad.
The other thing like you said was about finding love. Sometimes your true love can be right in front of you, but your mind is too clouded to notice it - like Theodore with Amy. You are too distracted by other things - relationships, society, lust, etc. In the end it was just two broken souls (Amy and Theodore) coming together and finding that comfortable space and connecting with each other.
Ok, will stop now :P
