You don’t know the probability, is the only thing wrong.
250 gem keys is nothing. There is an 0.12% chance of getting a mythic from one key. For future reference, you need to spend 2,500 gem keys to have a 90% chance, which still leaves a very wide 10% margin for failure. For VIP keys, you need around 275. Lots of people spent far more resources than you and still didn’t get it.
This is a gacha game. A slot machine. Your level, your guild, and how much money you spend have nothing to do with what you get. That level 8 newbie is an outlier. Rare. I didn’t get my first mythic until around level 400, and I know people that took even longer. The only way level is relevant is “you need keys”, so generally by the time you’ve reached certain levels you’ve spent certain predictable amounts of keys.
The game is not rigged towards new players. It’s rigged towards the house, like any casino. The devs bet setting this drop rate would cause a lot of people who don’t understand probability to spend money on gems that give them an almost 0% chance of proceeding. They won. The 900 gems were what, 75 gem keys? 6%. Your money was worth a 6% chance. You’ve got better odds of winning a free value meal in McDonald’s Monopoly, speaking per dollar.