Tanzu is a loaded term :) Are you talking about TAS (ex PCF) or TKG?

PCF

i wouldn't say it's on its way out. it's still in active development and very much supported

Why is it on its way out as a product? Is it simply not making money?

The scuttlebutt I hear is Kubernetes is stealing its lunch money.

Again, referring to what used to be PCF. Hence why the more modern Tanzu is K8s based.

PCF is still making bank but the industry has rallied around K8s. So growth has stalled but it has a happy customer base.

Unfortunately there’s no real equivalent (OpenShift is not really “it”) on K8s unless you’re assembling several products together with a lot of glue. Which is what everyone does, with varying quality.