I understand the rarity of diamond ore is due to the massive caves that expose tens of thousands of blocks, but I think this change had unintended consequences to every other aspect of mining.

The classic/tunnel/swiss cheese caves caves (the caves in the current version of Minecraft) still expose the same amount of blocks as they always had, but the chance of find a diamond ore per block exposed is the same as one of those massive caves, its possible to explore a massive network of these caves and find no diamond ore or just one or two veins, which in the latest update are most frequently 1 or 2 diamonds.

Shafting is even more broken, I have gone through entire unbreaking III Netherite pickaxes and not found a single diamond vein when shafting. Not only is the ore density at the optimal elevation approximately half of what it used to be, but the blocks you dig through take much longer to break, and since the veins are smaller, you are less likely to run into one on average! (if you pick the layer of a chunk that has the diamond ore in it, you are somewhere in the range of 15-25% less likely to find it since only 3-4 strips will expose the vein, instead of 4-5 strips on average.

Just to make sure I wasn't falling victim to horrid luck or some sort of cognitive bias, I surveyed the contents of 400 chunks and did some math to determine ore density in the latest snapshot. I then converted pre 1.17 diamond ore data to match the same units of measurement that my 1.17 measurements are in (diamond ores per 100 chunk layers) and the results are pretty telling (see attachment). Diamonds at peak concentration are 1/2 of that in current versions, and exposed blocks have 50% of ores skipped, meaning that they only have 1/4 the frequency. This is okay for the noise caves, but as I mention before, it's bad for small caves and shaft mining.

Note that the chart I provide is approximate, but the differential is so big that it irrefutably demonstrates that diamonds are too rare.