We don't know that any fighter is getting away with PEDs usage. Unless they come out and say it, and then provide evidence of it, we don't know.
All we know is who USADA has caught with banned substances in their systems. Even then, we don't know if they were using PEDs or they were contaminated.
USADA only tells us that they found something. They don't provide any further information about awareness and intention. To say that somebody is using something, I think you have to show awareness and intention, in order to say "that person is using this or that."
For example, if your significant other adds MSG (monosodium glutamate) in the food that she cooks for you, and you eat the food without a second thought. Can we say that you are using MSG? In my opinion, no. "Using" implies awareness and intent/purpose.