XML serialization has been around ever since .NET was released since it was so widely used back then. It’s still widely used, especially for legacy applications and services, even iTunes still uses XML to store library information. Benchmark results are for .NET 5 & 6.
The most popular serialization done these days is to and from the JSON format due to it being less verbose than XML and therefor more performant. This article shows how to get the best performance when serializing objects to JSON.