Have diamonds become even rarer in Minecraft?

I use the mine tactic to dig up to level 9 and then build straight up.

But somehow I can hardly find diamonds with this tactic. Did they do it so that you can find more diamonds in the cave? As if you just puddle straight ahead?

I think the diamond height is 11, not 9.

But they haven't really changed anything as far as I know

Most likely just out of luck. Sometimes I'd find half a stack of diamonds in under an hour and sometimes I'd find nothing in days.

Saw a couple of YouTube videos where one said level 9 is optimal.

I always look for mines that go down to y 5 then you will find more diamonds than stone XD