At my current shop, we struggle to maintain k8s clusters with an 8 person team. We inherited the debt of a previous team that had deployed k8s and their old legacy stuff was full of dependency rot. We have new clusters, and we update them regularity, but it's taken nearly half a year so far and we don't have everything moved over.
You do need good teams to move fast; and good leaders to prioritize minimizing tech debt.
I think the way we've approached it achieves the same goal as just giving each team their own cluster to avoid them messing up other teams.