Different languages also have their own culture and ecosystem, which are also valuable to learn in order to get a different perspective.
Some things that are taken as best practices are bad practices in other langauges and vice versa.
For example, lots of Java devs are against early and multiple returns to the point of absurdity, while in functional languages this is idiomatic and no problem at all.
Using different languages lets you see how different approaches work out in practice, so you can get a better view about which approaches work and which approaches are just cargo-cult nonsense.
Some things that are taken as best practices are bad practices in other langauges and vice versa.
For example, lots of Java devs are against early and multiple returns to the point of absurdity, while in functional languages this is idiomatic and no problem at all.
Using different languages lets you see how different approaches work out in practice, so you can get a better view about which approaches work and which approaches are just cargo-cult nonsense.