FSR and DLSS are not a perfect thing, they can only reduce pixel shader overhead but not geometric shader overhead.
Not to mention that the treatment has side effects and must be considered carefully.
As someone mentioned above, the use of the pipeline must be changed on a large scale, the current level of official technology is estimated to be necessary on the SRP in the URP to be possible.
This means that almost all existing assets have to be abandoned and rebuilt. From the current level of Unity3D construction, it is recommended to start experimenting at least from 2022.3.
A successful conversion will require years of processing, and eventually a one-time replacement of the version.
Then you can have motion vectors (new version of Unity), allowing the implementation of DLSS2.0 and FSR2.0.
Maybe include geometry and CPU overhead if it’s DLSS3.0.
But it’s too early to say all this, the effort required to replace from BRP to SRP is huge, for vrchat.