You're going to get crap if your hill to die on is that Kova is a deserved 4 times Champions League winner. I don't agree about just the finals thing, but when he's not starting any of the meaningful knockout games, that does suggest he was a squad player.
He's a great player. Before he arrived a few City players had even described him as one of the best they'd ever faced. But he's very, very lucky to have 4 CL medals.
Comparing his contribution to Foden, who had multiple injuries last season is pointless. In City's first run to the CL, Foden played every game, starting 12 out of 13, including the final, and he's already played a lot more CL knockout games than Kovacic.