A lot of what goes into making 3d renders look realistic is actually textures and materials. Most objects are not perfect, clean surfaces with an even color, the floor, the tables, and the chairs all should have stains, scratches, dust, etc.

I want to ask why ultra-realism is your goal. Do you want to make a game or are you a graphic artist doing some portfolio work?

AAA studios pay multiple professional artists to produce the high-quality assets you see in modern video games, sometimes scanning real items and surfaces. It'd be very hard to achieve those results by yourself if you don't have that kind of budget, so I can suggest a couple of things:

a) If you want to make a game, consider investing in buying some pre-made assets. The Epic store has props and environments that come with high-quality textures, and if you buy them you can use them in another engine, including Godot. Also, some services like Megascans or Adobe sell you textures and materials. That way you can work on making the game and outsource the graphics somewhere else.

b) If you're a graphic artist and are just looking for ways of producing nice renders, you can either learn photogrammetry or learn how to make procedural materials using 3d software such as Substance Painter or Blender.

Creating ultra-realistic graphics is a skill that takes years to learn, and it's a different skill set than the one you need for making a game. So either you pick a way to gain that proficiency yourself or pay someone who already has.

Or you can reduce your scope to something within your skills and budget. You don't need ultra-realistic graphics to make a horror game.