Career mode is NOT supposed to be that poor at racing....nor that easy................ Other games do ti fine, why can't GT? No damage is also ridiculous in a sim, smnashing into a wall, bumper car your way to first undermines GT's sim nature. Game needs a lot of work.
The Carrer mode is supposed to go until normal challenge only... if you want more you need to set your own races or play Seasonal Events (they will release soon)... or play online (that's where GT6 outshine the competition).
I agree the cosmetical damage is bad... really bad... it was just added for nothing because nobody care... but the mecanical damage is present and it makes a huge part of how the cars handle during the races... if you smashing into a wall in no time your car won't go over 50mps anymore (some cases it can't even run anymore).
Games needs a lot of work but you complain is something that already exists even in GT5... the only fair point is that the cosmetical damage need to get better (even so the Premium cars have a good cosmetical damage... the standards are really bad).