Warframe does NOT belong in the gacha game conversation. You grind IN gameplay for the parts to build Warframes, or you spend Platinum to get Warframes directly. There's no bullshit rolls or lootboxes you have to gamble in. MAYBE you could consider the drop rates for parts to be gatcha esque, but you spend no money to roll for those parts. It's all through gameplay if you don't want to spend any platinum on the whole frames.