SD-WAN is the most over-sold acronym of the last decade. It is also genuinely useful — in the right shape of business.
If you have three or more sites, a mix of fibre and broadband connections, and applications that have moved to the cloud, SD-WAN is worth a serious look. It will route voice traffic over the best path, push bulk traffic onto the cheapest, and fail over to 4G/5G in seconds rather than minutes.
If you have one site and one connection, SD-WAN is a marketing exercise. A decent firewall and a 5G failover dongle will do everything you need.
The honest test is to ask your supplier to demonstrate the cutover in real time. If they cannot pull a cable and show you traffic moving, what you have bought is a routing protocol with a logo on it.