[2023] CK3 Keeps Crashing

You mean a campaign that you started two years ago real-time? If so, you will certainly be having compatibility problems, you would have been on patch 1.3.x or 1.4.x at that time - we're up to 1.9.2.1 now - more than 20 patches later!

If you know what patch you last played it under, you could revert to that game version in the Steam Betas tab for the game.

Otherwise you'd really need to start a new campaign.

All the best!  

If that campaign has been saved under a new patch, you won't be able to play it under an old patch, no. You'd need to use the save game file from before, if you still have it.