Why would Alexander-Arnold not leave then? By this logic he should have gone last summer. Fact is he's better than every other English prospect and proved his value. Klopp also gave Kevin Stewart and Jordon Ibe plenty of chances to show their value. Joe Gomez is yet another. Brewster was already training with the first team, so clearly Klopp liked him, and the appearances are just around the corner.
Anyone can get the minutes if they're good enough. CL Finalist this year proves that 100%, there's some guy who was just playing at Hull and another who was just at the Liverpool academy in the team now. If Brewster leaves, it definitely isn't only about playing time. It's about a fresh start, one away from these kinds of problems, and no good supporter would begrudge him for leaving. Nobody, and I do mean nobody, should be angry about it.
The simple fact is, bringing up playing time as it relates to Liverpool, is pretty false when there's a 19 year old Liverpool academy player about to start in the CL Final, who proved they were the best right back in the team. If Brewster decides to stay there and isn't loaned he will play at least 12-15 games next season.