Arithmetic compression, Huffman compression, Lempel-Ziv compression, etc are all excellent at compressing sequences produced by small programs. Things like:

1010101010101010 110110110110110110 1011011101111011111

...etc.

Those compressors (crudely) implement a computable approximation of Solomonoff induction without iterating through programs that generate the output. How they work is not very relevant here - the point is that they act as general-purpose compressors - and compress a great range of real world data types.

The complaint that we don't know what types of data are in the universe is just not applicable - we do, in fact, know a considerable amount about that - and that is why we can build general purpose compressors.