I'm not sure that's the case. Hardware Unboxed did analysis with RTX on and off in Metro and explained why it looked better when on but the differences seemed minimal to me. They talked about 'the accuracy of the shadows', which I don't really care about. You can judge for yourself:
Paid for reviews, cba'd to watch that one in particular but I watched a couple of videos and there were comments about how without raytracing the people not directly under the light in one scene were too bright and with ray tracing only those directly under a light were lit up as it 'should be'. It was just bull ****, aside from the fact that it was a small space and we've had games for a decade that can light up things closer to a light source more or show a cone of light and those underneath as better lit, it's the fact that with ray tracing turned off Metro has the lighting absolutely and completely purposefully neutered to make ray tracing look better by comparison.
This is what I've been saying for years on ray tracing, ray tracing vs 90s rasterisation was night and day, ray tracing vs absolute best case rasterisation and 'fake' lighting look extremely close to each other. The only way to make ray tracing look genuinely hugely better is to cripple the lighting without it.
Even Nvidia's first demo of it on launch they showed the one green room with lighting from the early 00s vs ray tracing and marvelled at the improvement, thankfully Tomb Raider was too early to have it's lighting completely neutered to make ray tracing look better.
Ray tracing in Metro doesn't look any better than Tomb Raider, it just looks like effectively no improvement over the normal lighting modern games have. Metro had time to get crippled by Nvidia.
This is also what I've said in recent threads, the reason I go with AMD is their messing around doesn't harm all gamers, it gives a benefit to everyone. nvidia have decided even if you're an Nvidia user you can now play Metro with crippled lighting if you don't have an RTX or you don't have the performance spare to turn RTX on. So a worse experience for 90% of Nvidia's own customer base and for all AMD users just to make ray tracing look better by comparison. Tomb Raider as said added ray tracing and only for Nvidia users, but the base game wasn't crippled in quality just to make it look better. I'm fine with that, Nvidia isn't, they want to make it a worse experience for people who have paid them hundreds for cards if they can't use ray tracing. Nvidia are terrible for gaming and gamers in general.