We had single-datacenter resiliency (meaning n+1 on power, cooling, network + isp, servers) and it was fine. You still need offsite DRS strategy here - this is one of the things having that hybrid cloud is great for: you can replicate your critical workloads like databases and services to the cloud in no-load standby, or delta-copy your backups to a cheap cloud provider for simplified recovery in a disaster scenario (ie: entire datacenter gets taken out). The cost of this is relatively low since data into the cloud is free and you're only really incurring costs in a disaster recovery scenario. Most virtualized platforms (veeam etc) support offsite secondary incremental backups with relative ease, recovery is also pretty straightforward.

That being said I've lost a lot of VMs on ec2 and had entire regions go down in gcp and aws in the last 3 years alone, so going to the public cloud isn't a solves it all solution - knock on wood the colo we've been using hasn't been down once in 12+ years.