Multicloud Networking can be extremely reliable. It all depends on configuration. A single tunnel between our networks is the least desirable, but multiple tunnels between your location and at least two POPs on the Total Uptime platform increases reliability significantly. Add BGP for dynamic routing and you can achieve 99.999% reliability.
Many providers, such as Amazon Web Services (AWS), design their platforms for high reliability VPN usage. For example, with AWS, a very common implementation is a redundant pair of tunnels to two endpoints. This means between AWS and the Total Uptime platform you can have 4 tunnels split between two of our POPs. Coupled with BGP, the level of reliability is absolutely five nines based on our experience.
Azure is not quite as good because they seem to perform maintenance on their VPN VMs very often, perhaps as often as you see updates available for your Windows 10 machine, so this causes short outages on a regular basis. But with a dynamic routing protocol like BGP, failover is fast and the impact to your availability via the tunnels is extremely low.