It's a bug, although it should be a feature. 5E removing the Wizard's ability to learn any spell always irked me. It's going to be fixed eventually, but I will love it for as long as it lasts.
Wizards have never been able to learn any spells they want. They have a dedicated Arcane spell list. This was how it was in table top or any of the games, like the original BGs (2e ADnD), and Neverwinter Nights 1 & 2 (3.0e, 3.5e).
What 5E
HAS changed, is the splitting of the Sorcerer and Wizard spell lists. In 3/3.5e Sorcerers and Wizards shared the same spell list. This is no longer the case in 5e (Wizards have a larger and better spell list).
