An update was released to fix the a14 freezing issue, update and it should help.
As for what happens if you don't update. You'll not get any new features or fixes. You'll not get any security patches so viruses, exploits and hacking becomes a possibility. There's a chance apps might crash or have issues due to using old software without bug fixes. There's even a chance phone calls and texts might stop working, if your cell carrier tweaks how they work, your phone might not get the update to continue working correctly. It's could also potentially make your phone easier to steal. Updates some with anti theft improvements.
It's best to install updates when you get them. If an issue occurs, report it and samsung should release an update later to fix it.
The a14 issue was really annoying, but around 2 weeks after it started, a fix came out
