Just a side note:
TF2, released in 2007, hasn't had lootboxes till 2010. Valve was not even the first game to have them.
spoiler
FIFA was 1 year ahead, but not the first one either.
Also, TF2's lootboxes are not the same as Dota2 and CSGO/CS2. TF2 weapons have an actual change of gameplay to them while Dota/CS has just skins. Not to mention, you can get all weps in TF2 by just playing the game.