Why can't existence be mostly good?
Enlightenment &amp; the path to enlightenment (such as meditative jhana) is a higher &amp; better pleasure than any pleasure that can be experienced in ordinary life. 

This is the simple, accurate &amp; correct way to view enlightenment. 

Please refer to this link.


  
  Bhikkhus, there are two kinds of pleasantness. What two? Household pleasantness and the pleasantness of one gone forth. Of these two, the
  pleasantness of one gone forth is better.
  Bhikkhus, there are two kinds of pleasantness. What two? Sensual pleasantness and the pleasantness of giving up sensuality. Of these
  two, the pleasantness of giving up sensuality is better.
  Bhikkhus, there are two kinds of pleasantness. What two? The pleasantness with substratum and the pleasantness without substratum.
  Of these two, the pleasantness without substratum is better.
  Bhikkhus, there are two kinds of pleasantness. What two? The pleasantness with desires and the pleasantness without desires. Of
  these two, the pleasantness without desires is better.
  Bhikkhus, there are two kinds of pleasantness. What two? Material pleasantness and immaterial pleasantness. Of these two, immaterial
  pleasantness is better.
  Bhikkhus, there are two kinds of pleasantness. What two? The noble pleasantness and the ignoble pleasantness. Of these two, the noble
  pleasantness is better.
  Bhikkhus, there are two kinds of pleasantness. What two? Bodily pleasantness and mental pleasantness. Of these two, mental
  pleasantness is better.
  Bhikkhus, there are two kinds of pleasantness. What two? Pleasantness with joy and pleasantness without joy. Of these two,
  pleasantness without joy is better.
  Bhikkhus, there are two kinds of pleasantness. What two? Pleasantness on account of agreeability and pleasantness on account of
  equanimity. Of these two, pleasantness on account of equanimity is
  better.
  Bhikkhus, there are two kinds of pleasantness. What two? Pleasantness on account of concentration and pleasantness on account
  of distraction. Of these two, pleasantness on account of concentration
  is better.
  Bhikkhus, there are two kinds of pleasantness. What two? Pleasantness with joy for an object and pleasantness without joy for
  an object. Of these two, pleasantness without joy for an object is
  better.
  
  
  Bhikkhus, there are two kinds of pleasantness. What two? Pleasantness on account of an agreeāble object and pleasantness on
  accout of equanimity for an object . Of these two, pleasantness on
  account of equanimity for an object, is better.
  
  Bhikkhus, there are two kinds of pleasantness. What two? Pleasantness born on account of a material object and pleasantness
  born, on account of an immaterial object. Of these two, pleasantness
  born, on account of an immaterial object is better.
  


As for your other concerns, they are unrelated to Buddhism. Buddhism is not for people who believe ordinary life can be pleasurable most of the time. Buddhism never ever states all people must follow the Buddhist way of life.