> Sure, but that's not what people mean when they say cross cloud. It usually implies running active workloads.
For workloads large enough to justify load balancing, that isn't that hard. Things should only rarely care which "cloud" they're running on. The amount of the load assigned to each one is a knob you can turn.
For workloads smaller than that, the primary way to achieve redundancy is failover. Whether it's worth the cost and complexity of making that happen automatically instead of manually doesn't have a universal answer.
But "just use a more reliable provider" doesn't work if being down matters. AWS, Azure and Google Cloud have all had major outages. More than that, sometimes a piece of equipment fails in a way that takes adjacent equipment with it, or there is a fire or a burst pipe. They call it "cloud" but somewhere there is physical hardware under your bits and it can fail. Each failure may only affect a limited number of customers, but those customers can include you. If your systems can't be down, you need a plan in place to have them running again somewhere else in short order. And putting the system you use for this on a different provider can save you from a major provider outage.