I'd say it's hard, but it has a very natural difficulty curve. For example, the first level may seem quite hard at first, but then you'll get better each run and you'll get upgrades which will make it easier each subsequent time you play it. Everything kind of just clicked for me after a while.
I'd say it's a bit easier than Bloodborne but I also feel like I'm better at shooters than I am at the Souls games. Maybe
@tenken00 can also chime in on the difficulty. The only thing is you will likely need to block off a few hours of time to do a full run, otherwise you will have to pause and put it in rest mode to resume later because there is no saving and loading (aside from one "save point" you reach at the halfway mark of the game). The developer hinted that they were going to add some sort of save feature, but as of now I don't think they have added it yet.
I recommend Returnal wholeheartedly. The gameplay and controls are top-notch, it has an interesting story, and the graphics are fantastic. So far it's been my favorite PS5 game. I waited for it to be on sale for $50.00 because I had the same initial concerns you had. However, knowing what I know now I would have paid the full $70.00 for it.