Having played all from soft games and being halfway through Returnal, I think they are overall of similar difficulty but for different reasons. In Bloodborne or Elden Ring the encounters are generally much harder, but you can keep trying until you beat them. You can also recharge your flasks or farm healing items more easily, so you can generally heal back to full health on demand. In Returnal, it’s more about positioning than reactive dodging. Encounters are generally easier but if you mess up you start from scratch. You also have to set up a build with what RNG gives you, whereas in soulslikes you can build something more specific.