I've learned some time ago, that GT and other grinding games, you have to play from the beginning, to make use of any glitches. In case of GT7, Tomahawk + Tokyo and opening all the invites made sure I don't have this problem anymore. Similarly in GTS, I've sacrificed one weekend for the pit entry glitch to level up to level 50, although I should have sacrificed two weekends, as I didn't have enough money to buy all the new cars they added later. But at least I didn't end up like people playing honestly for years just to end up at level 47-48 with no chance to reach 50.
On the other hand, when you have all the invite cars and your 5* ticket gets wasted on an invite, it's also infuriating. So all in all, this is a very bad system.