Could it be that the reviewer just didn't enjoy Remnant 2 as much as others? Just an hypothesis
It could be. But at same it could also mean the individual who reviewed the product doesn't understand anything about game design and is not looking at the game objectively. There are far too many reviewers who let their emotions play a part in reviewing a product instead of actually giving it a thorough analysis.
For example - I cannot stand golf games. So what happens if I am going to be reviewing a golf game, an automatic 5/10 cause I hate golf? No, if I am smart and understand how to properly judge things objectively, I'll put my emotions aside and see how this golf game excels or fails at its gameplay mechanics and execution. You can still be a bit subjective for sure, but you have to learn to be more objective than anything when reviewing a product and a lot of reviewers really lack that.
They are either too busy with their shitty political agenda insertions or crying about how a mechanic is bad without actually understanding how it works in the first place. Yes, there can be bad mechanics, but you can't say it's a bad mechanic unless you truly understand it.
If someone gave Returnal a score of 5 or 6 out of 10, that just simply means they understand nothing about the game's core gameplay design. And a review like that should never be taken seriously. Or they are doing it to feed the fanboy wars.