I'm not going to link anything here, but just to be clear, you can search for Yugioh booster pack TCG and open any official info page and you will find this sentence.

Each main series Booster Pack is guaranteed a Rare, 7 Commons, and a ninth card which will either be another Common or a foil card (Super Rare rarity or higher).

I have some unopened packs that I'm so close to opening up just to prove you wrong but that would be a huge lol.
There is even another simple solution you can do. Go on youtube search ANY pack opening video and that's it, I don't think you will need more proof after that.

Also, for booster boxes it says this (on wiki):

If a customer buys a booster box of a pack that contains a Ghost Rare card, they have a 1/36 chance of getting one. The probability of getting {\displaystyle x} Ghost Rares in one box is {\displaystyle (1/36)^{x}}.
Boxes are cheaper per pack and per card than buying booster packs. A booster box of 24 booster packs...

While I didn't find any conclusive info for Secret rares, I'm sure they are maybe two times as likely to show up as Ghost rares. So yeah, there is a decent chance to not see a Secret rare in a box although there is almost always 1 (from my experience).

10 year bro? I mean, what have you been doing for those 10 years then? Not buying packs? xD Just teasing ya :P, but still, you are wrong.

There is other info suggesting there is a limited amount of commons in a pack but, as I said. The easiest way to confirm this is to watch a video of someone opening packs for half an hour xD.