The leaps in this writing pain me. There are other aspects, but they’ve been mentioned enough.
Vendor lock in does not come about by relying only on one cloud, but by adopting non-standard technology and interfaces. I do agree that running on multiple providers is the best way of checking if there is lock-in.
Lowering the level of sharing further by running per-service and per-stage clusters, as mentioned in the piece was likewise at best an uninformed decision.
Naturally moving to AWS and letting dedicated teams handle workload orchestration at much higher scale will yield better efficiencies. Ideally without giving up vendor-agnostic deployments by continuing the use of IaC.