Dynamic lighting already exists. Look at Phasmophobia, it's probably one of the heaviest Unity games because it uses it everywhere. Basically every light in that game is able to cast shadows, and it's got a lot of lights. Doesn't have any of the RT noise or lag too.
edit: it doesn't come cheap though, they had to do some downgrades to port it to consoles. Interior candles for example, they're no longer interactive.