I’ve been in your shoes (The Diary of the FTP who finished 53rd in legendary). It was 1 year and 9 months for me until I got my first 5* from pulls but it was Hel! Were there any moments during these 21 months when I was discouraged? Yes. But my love for the game and my alliance kept me playing.
You’ve had bad luck with pulls but they are the best way to progress in the game. The mistake I used to do in the past was to use EHT, Atlantis coins and gems right away when I had enough for a pull.
It’s been just two months since challenge coins have been in the game. My advice is to choose an event from which you want the 4* heroes and save the coins for it. I learnt the hard way that trying for every single event but not concentrating on one is a bad idea.
Don’t get discouraged. You’re in a very bad streak but this means that a good streak is coming. Good luck!