I think Calabria is getting a disproportionate amount of blame for Verona's goal. I think Kalulu was out-of-position, while Calabria was playing too narrow (that's his fault) but I also think that Tomori and Theo got their marking all wrong, why wasn't someone on that backpost? You could even ask why Maignan didn't come out for the ball? Calabria looks slower this year than last year, though, he looks like he's injured when he's running. He was never fast (which is what I think will hold him back from being an elite European player rather than just an elite RB in Serie A), but he doesn't look comfortable. I wouldn't be surprised if we hear that he's had some injury this year that he's been playing through.
That goal was a mistake, yes, but it's weird to me that whenever a player makes a mistake, we have to sell them and move on. We are going to concede goals. Hopefully not for the rest of the season, but, I promise you, this team, even if it reaches its zenith, will concede goals. All teams do.
Also, when you make attacking passes, you're going to miss, you have to take risks, and our tactic of using the long ball (which Liverpool do, a lot) to negate and/or scare a team that wants to combine a press with counter attacks, not saying our passing is perfect, but I think we are a little unfair with some players sometimes.