I already have a bunch of basic PBR textures for materials such as metals, wood, and tiles. However, I am now trying to make textures for objects such as computers, kitchen appliances, and vehicles. If I use Texture Paint on top of the PBR base materials, it will look horrible, and I don't know how people will react to me taking photos of everything I see.

https://barium.ai/​ can generate pretty much any material, although it can't do things like roads with painted lines (although you can do a road material then a line paint material separately).

If I use Texture Paint on top of the PBR base materials

What is Texture Paint?

I don't know how people will react to me taking photos of everything I see.

Photos of objects are still useful. PBR doesn't mean “can't use photos”. In general the photograph will contain the color, you will still need to manually author the metallic and roughness texture for it. Almost everything nowadays is a scanned in 3D asset from the real world.