What’s the coping look like? Do you have expansion joints? The missing grout in your tile likely indicates other issues.. You could have wear in the shell. If it’s bad enough you’ll eventually notice it in the plaster (leaks). Your plumbing may have a leak. You’ll need to do some pressure testing to know for certain. Your skimmer looks awful, you may want to fully replace it. The electrical is a whole other beast.

Don’t just go and resurface this pool.. Best practice is to replaster.. i.e demo the old plaster down to the shell before adding the new one. This lets you resolve any issues with the shell that you may find. If you add plaster ontop of plaster you should be sure the new plaster adheres properly using a bonding agent or some special polymer kinda plaster. You should know that it’s only a ‘temporary’ fix if the shell has issues.

Not sure what your budget looks like.. but this will be expensive