Some fans are frustrated because they are too confident that their tactical and personnel choices would have been better, despite having no experience whatsoever in coaching and managing at any level, let alone at top top level. They are completely unaware of their limitations, erroneously believing they know better.
Your suggestions range from ludicrous to dubious. I'd have tried Nunes, I like him, but there are obvious concerns about his first touch and ability to pass the ball around like a proper DM or CM in a Pep team. Starting kids in midfield against Juventus is not a genuine option. O'Reilly needs more experience. He played against Spurs, didn't show he has enough to start at this level right now when we are desperate for more points. The team that started vs Forest and played really well is the best right now, but Ake and Akanji got injured.
The problem with our midfield is that those who know what Pep wants from them and can implement his instructions, lack physicality, whereas those who have legs, lack experience and perhaps the ability or brains to do what Pep wants from them in that part of the pitch. There are trade-offs. Some fans think that having legs is more important than experience, technique or intelligence, but this is something that Pep disagrees with.