Pretty much what it says. I'm aware Windows 7 is super old and is indeed slated to no longer operate Steam in the New Year, hence my shopping around for an upgrade, but it's frustrating when such an update breaks your setup without warning. After doing a few reinstalls I found the 2022.9 folder can still open the Launcher, but the 2023.14 folder has the following error:
Googling suggests this is an issue with other applications attempting to still run on Windows 7, so I think that is the case. I can still open EU4 directly by navigating into the Steam folder, but I lose all access to mods or achievements. If Paradox intended to drop such an update which would remove Windows 7 support, an announcement on the forums would have been nice, or perhaps some synchronising with Steam's well-announced plans to discontinue support.

Googling suggests this is an issue with other applications attempting to still run on Windows 7, so I think that is the case. I can still open EU4 directly by navigating into the Steam folder, but I lose all access to mods or achievements. If Paradox intended to drop such an update which would remove Windows 7 support, an announcement on the forums would have been nice, or perhaps some synchronising with Steam's well-announced plans to discontinue support.