Minecraft problem? - 2

I like to play Minecraft Survival and have a lot of ores. Over 64 gold and even more iron and coal but also more than 10 64 Redstone and also over 64 Lapis Lazuli. Unfortunately I have no diamonds and emeralds. I somehow can't find any diamonds either when I'm at a height where they could occur. I have been to different gorges twice and have found almost every ore but no diamonds and emeralds. Somehow it seems to me that they are TOO rare. I also have a long time I didn't find any diamonds or emeralds. Why are they so rare to find. But I also need diamonds to craft magic tables etc. But also to mine obsidian and get into the Nether. I could easily get emeralds from villagers But I really don't know what to do, am I just unlucky and can't find any diamonds?

You have to go to level 5 in a mine, you will find more diamonds than stone xD

I think there are diamonds only at levels 5-15

Do you mean mineshaft or what? I've been at an altitude between 5 and 15 almost the whole time.

So most of the slides and such are at level 12, as well as below and above nearby.

This is at least the case with most maps.

For example, I messed up very long corridors at height 11 and still couldn't find any.