Qweesdy maybe sure, but it's fun as hell to build something that massive and field it with support. Even if it is technically inefficient, it's still got more shields and power than anything else in the server, and turn rate doesn't matter when you can have turrets the size of moons to fire instead.
because of this, the likelihood of such a titan getting destroyed is miniscule unless directly assaulted for a few hours. And now with effects, these ships can enter warp speed with not too many overdrive modules and escape any dangerous situation.
FINAL EDIT: why do you call it a pointless waste of time? building ships can be fun and challenging. Either recreating iconic vessels or coming up with a unique faction mothership, the time put into it imo can be worth it.
for the credit issue. An old and tiny server I used to play on had the admins spawn in larger ships if the players could provide the additional credit cost in a block. Weird system, but it worked at making some fun fleet battles