This is not complicated, I promise:

1. This is the original Steam Deck, not the fancy new OLED. That device was not perfect.
2. It especially wasn’t perfect over 100 software updates ago, and they certainly had their deck several major updates before I did. idk about you.
3. Reviews have context. They aren’t just rating all things on a general scale of 1-10. Like saying the Steam Deck OLED is a 9/10 isn’t saying “well it’s good but not as good as Elden Ring, which is a 10/10, you should buy that instead!”. Every review (and therefore review score) is relative to the needs it intends to fulfil. The Playstation Portal is a device for specific people with specific needs, and the Steam Deck is for different people with different needs. And so the Portal is reviewed on a scale of “how well does it satisfy the needs of the people it is for?”. In that regard, an 8 makes sense, even if you are not one of the people whose needs it is designed to fulfil. Basically, not everything is made for you specifically.