Ever since 1.20.2 when you click on Resource Packs page, the game can easily freeze and load the page for a minute or so. It depends sometimes it takes only few seconds, but after a moment dozens of seconds again. Even if it takes less than few seconds, before 1.20.2 it was instantaneous!
I have many folders inside resourcepacks folder, around 50 resource packs folders/zips and another nested folders. I have minecraft saved on HDD. All these are propably the factors slowing down the loading, but as I said, the loading worked instantaneously in previous versions. So why not in 1.20.2 and above?
I think the main reason is that you can't have many resource packs in a folder inside the resourcepacks directory of the game like before, else you experience the game lagging every time you open or the game loads things regarding resource packs. In older versions that was no issue, but now the game does some unnecessary loadings of things that aren't resourcepacks it seems.

Overlays
It is as if the game tried to get through every folder and file there is instead of just picking on the main aspects like picture and pack.mcmeta. As I thought about it, I also assume the issue is related to new overlay system in packs, because the game must now recognise more "sub-packs" in the resource pack itself. The issue is that it seems like it is checking for things it doesn't even need to, because it really just needs to really know the content of almost only one file that is directly in the first folder and that is pack.mcmeta, not every other folder.

In the logs it gets stuck on lines like:

[18:09:02] [Render thread/INFO]: Found non-pack entry 'D:\Users\DelimanCZ\AppData\Roaming\.minecraft\resourcepacks\#archiv', ignoring
[18:09:55] [Render thread/INFO]: Found non-pack entry 'D:\Users\DelimanCZ\AppData\Roaming\.minecraft\resourcepacks\#versions', ignoring

I was working with resource packs in the past, so it is very convinient to have sorted folders with resource packs inside the resourcepacks directory. I will include some folders in here so you can try yourself (extract this to your resourcepacks directory): https://drive.google.com/file/d/1gESaV3yavJ5dtbC9YNmkRQX6nh59xhH3/view?usp=sharing

Video demonstrating the issue: https://www.youtube.com/watch?v=G2It_ueXeJw
Video demonstrating that the issue is not caused by using better launcher previously: https://youtu.be/Bre7CgdnYMg