Shaw has branded it "toxic" and supports manager Ruben Amorim's attempts to clean it up.
"It's not hard to see from the outside what it's been like," said Shaw from their US preseason base.
"A lot of the time I've been here over the last few years it's been extremely negative.
"It can be quite toxic, the environment, it's not healthy at all. We need an environment that's healthy, that's positive, that's got good energy and happiness. When you have all those things, you feel free and you express yourself more.
"Ruben brings demands. Mentality is a big thing. He talks a lot about it.
"He demands 100% and doesn't want anything less. If someone's doing 85-90%, it's not enough. I think, especially this year, if you're not doing the right things, you won't play."
Shaw also insists the manager needs the full support of senior players to bring through the much-needed change.
He also said, "The more experienced ones need to be demanding more, day in, day out.
"The levels in training, keeping to the times of when we're doing this or that, making sure no-one's coming late.
"The manager's not bothered. He doesn't care who the player is. That's how it should be. Whatever he wants, as players, we have to be delivering – and we are fully behind that."