I simply think they have a much better roster than us. Pound for pound it's probably Skriniar, maybe Bastoni (though I struggle to see where), and one of our midfield who get picked in a joint XI tbh.
I meant more in the sense that Liverpool isn't so much better on paper as opposed to Manchester City (or even Chelsea), but it's more of a manager's team. Remove Klopp and you have a side that doesn't look so scary. Their best player is Salah who wasn't really a world beater in Serie A and Roma fans were calling his sale a genius move as he kept missing most of the few chances they had each game and disappeared in most games against camped defenses. Yet he's a Ballon d'Or contender under Klopp!
I'm pretty sure Liverpool would be extremely willing to take Skriniar, De Vrij, Lautaro, Bastoni, Barella, Brozovic, Hakan (in this form) and Handanovic.
Forget the transfer market and the different replacement cost structures, viability assessments etc, if these guys were available for this season, they'd be trying to poach them all.
Mixed XI is complicated due to formation differences.
In a 3-5-2, I wouldn't even take Van Dijk from their defense. It gets tricky with the wing backs as individually theirs are a better fit but I'm not sure if I take Perisic off this team.
Three in the middle comes from us, with Thiago challenging the Hakan position when fit and he's not really fit very often. Even the bench choice gets to be Vidal and not Keita.
In the attack, only Firmino can play the 3-5-2 position, so their two main offensive players are out.
So we can only consider TAA and Firmino to improve our current season's side from them individually, unless Thiago is somehow free from injuries and regains form. And I'm not even sure if Inzaghi would use Firmino that much. He's just not there this season.
If we go with their 4-3-3, their attackers are the main players but the #9 is Lautaro, not Firmino.
Three in the middle, as before. They have no player that improves us. We have at least 2 that improve them.
Four at the back gets tricky, they have both full backs and then it's a toss with Van Dijk who has been off form for months now, but even if you put him there, the other center back is ours. And so are the next two. And I challenge that Bastoni could hold that LB spot but it's speculation at this stage as he hasn't really played much there apart from Parma.
Alisson is really clumsy and no one in their right mind would pick Alisson over Handanovic unless you're thinking about 2-5 seasons ahead. Presently, that's just it.
Best case scenario for Liverpool, 6/11 of their players are in: Van Dijk, Robertson, Arnold, Thiago, Salah, Mane.
They have us in CL experience, they're a more gelled team, coach is brilliant and takes 150% out of his team whereas ours is in unchartered territory. And that matters a lot in Europe. Our squad is on a similar level and if we had the experience collectively (individually we aren't lacking that much when you count World Cup, Copa America and Euro, plus the EL campaign) I'd call it a wash, but the Klopp factor is just too much to handle.
P.S: I responded because you were talking about something else entirely from the original point