That's like saying that "physics simulation is the only technique that produces accurately shaped water streams" - technically true but generally not a sufficient improvement over the shortcuts currently in use to make up for the downside that the technically most precise method is slow as fuck.

Game making is at all levels finding shortcuts and simplifications (even games about the real world are riddled with simplifications, if only the gameplay rules being a simplified version of real world interactions because otherwise it would be boring as shit) and in the visual side of things those are all over the place even with RT (the damage on the walls, the clouds in the sky, the smoke rising from fires or the running water on the streams aren't the product of Physics Simulations but, most likely, the use of something like Perkin Noise or even good old particle effects to fake it well enough to deceive human perception).

Yeah, sure RT is, technically speaking in terms of vidual fidelity alone, better than the usual tricks (say, using an extra rendering step for the viewpoint of the main reflective surfaces such as mirrors). Is the higher fidelity (in, remember, a game space which is in many other ways riddled with shortcuts and simplifications) sufficient to overcome its downsides for most people? So far the market seems to be saying that it's not.

Depends on how you define "accurate". Even full ray tracing is just an approximation based on relatively few light rays (on an order of magnitude that doesn't even begin to approach reality) that is deemed to be close enough where increasing the simulation complexity doesn't meaningfully improve visual fidelity, interpolated and passed through a denoising algorithm. You can do close enough with a clever application of light probes, screenspace effects, or using a second camera to render the scene onto a surface (at an appropriate resolution).

Reflection probes are one way. Basically a camera drawing a simpler version of the scene from a point into a cubemap. Decent for oddly shaped objects, although if you want a lot of them then you'd bake them and lose any real time changes. A common optimisation is to update them less than once a frame.

If you have one big flat plane like the sea, you can draw the world from underneath and just use that. GTA V does that (like ten years ago without RT), along with the mirrors inside. You could make that look better by rendering them in higher resolution.

https://www.adriancourreges.com/blog/2015/11/02/gta-v-graphics-study-part-2/

Where RT is visibly better is with large odd shaped objects, or enormous amounts of them. I can't say it's worth the framerate hit if it takes you below 60fps though.