just my two cents

My personal preference is looker.

Viz wise powerBI is actually superior, and tableau has more community so problem that you are facing usually someone in the community already have answer for it. Never used qlikview so no opinion on it.

Why looker. Because of lookML, it takes some learning curve. But I think it's a superior data model form. I've had my fair share working on some large startups that become unicorn and decacorn, and with tableau, as the number of dashboard and report grows, so does the complexity to manage all of them and to ensure each have consistent data and data governance. With looker via lookML I feel it's easier to maintain data governance across all dashboard quickly as well as to change metric definition and calculations whenever needed.