I recently created a new Minecraft world in preparation for 1.16. I went in to the nether and i could not find a nether fortress i looked for 3 hours finding loads of the new structures. i then decided to use spectator mode and flew in all 4 cardinal directions and did loops around my portal. After around 2 hours of this i found one  about 10,000 blocks away from my portal. i decided to make a few more worlds to test this and I rarely find them. I have only tested 4 worlds so i may have just been incredibly unlucky, but i think that the new biome distribution may have stopped some of the fortresses spawning. This is really frustrating as the nether fortresses are required for all of the end game content. I am now considering restarting and abandoning all my progress.