As YoshiP said in the interviews this new Zodiac Systyem is another method to obtaining high level weapon. It's an option the players can choose.

1) From end-game dungeon - Bahamut's Coil
2) From Leviathan Ex (upgraded)
3) From upgrading your existing relic through this zodiac system, atma, etc...

If #3 is too hard for you, you still have option 1 & 2. No one is forcing you to get your relic upgraded, it's meant to be hard and long.
Do 1 & 2 and for 3 just do fates whenever you see them while doing other stuff, if you're lucky you'll progress. If you're grinding just #3 and complaining about it then that's your own fault.

However I do agree that the RNG factor for the drop rate is too extreme, they should place some sort of system where drop rate will increase say 0.1% per fate completion. This will at least take time but will also increase the drop rate. Only problem with this is it needs to be stored server side and that can lead to more processing with amount of players running FATE's right now. If they put that information on client side, people can hack it. Either way it still depends on the RNG, so those that are lucky will get with 1 try, those that are not will take 300 tries, even if it increased the chance by 50% you still have a 50% chance where it won't drop, if that continues, playesr will still complain lol.