ASN.1 has support for ISO 2022 as well as ASCII and Unicode (ASCII is a subset of Unicode as well as a subset of ISO 2022). (My own nonstandard extensions add a few more (such as TRON character code and packed BCD), and the standard unrestricted character string type can be used if you really need arbitrary character sets.) (Unicode is not a very good character set, anyways.)

Also, DER allows to indicate the type of data within the file (unless you are using implicit types). Protobuf has only a limited case of this (you cannot always identify the types), and it requires different framing for different types. However, DER uses the same framing for all types, and strings are not inherently limited to 2GB by the file format.

Furthermore, there are other non-scalar types as well.

In any of these cases, you do not have to use all of the types (nor do you need to implement all of the types); you only need to use the types that are applicable for your use.

I will continue to use ASN.1; Protobuf is not good enough in my opinion.