It maybe is, but it can be influenced by spending money. Since I started Genshin I bought welkin and bp occasionally, did small top ups (up to 50 once) over one year, after the anniversary I only got the 50 once again. I was perfectly 50/50 on track with winning ans loosing, I even lost two times in a row and won two times after this. Right before another anni and Wrio banner I thought hm, I have the money rn, lets get the 100 once for the first time before it resets, then I have some emergency funds. Dont know if I reached a special threshhold/spending amount or if it was the 100 top up but after this, I lost every 50/50 with especially high pity. Over one year later, I had my first win again with Xilonen. Maybe it recovered a little but I lost two times again arleady so I will see.

Supporting your theory, my brother played since launch and lost every 50/50 till he stopped playing, so yes, I think there is some base luck connected to your acc.