As someone who hasn't got to 50 yet either, I find it baffling you could have got this far without finding the fun - and that to me is a strong indicator that this may not be the game for you. I mean sure, there is going to be more challenge at endgame, and I'm looking forward to running raid content, but I'm also loving what I am doing now. In fact, I've slowed down leveling on my main job because I don't want to get to endgame too soon. My typical routine is daily beast quests on main class, daily GC craft hand-ins, playing another class through a few leves, grinding for mats if I feel like it, doing something on DF if i feel like it. I don't imagine level 50 is going to be hugely different, other than I'll be spending time focusing on gearing and progressing my main job too.

If I wasn't having fun at this point in the game, I would totally be quitting the game and finding something more fun to put the sub fee towards. maybe try a single month to make that push to 50 and see if you have more fun then, but honestly, from what you've said I think that may be wasted time and money.