Yes, it depends on content and won't do much for grainy surfaces. I don't have AAA game quality textures to compare, but I think for usual textured model it is still worthwhile. eg. this https://milek7.pl/.stuff/somelocotex.png weights 16MiB uncompressed, 5.1MiB as PNG, 5.3MiB as DXT5, and 2.1MiB as DXT5-in-LZ4. (mipmaps included in DXT5)
>PS I think that BC could be massaged at compression to be better compressible, and i think i read something about that. Don't remember.
EDIT: RAD page states that "BC7 blocks that are often very difficult to compress", so that might be also a factor why my DXT5 test compressed much better than your BC7.
EDIT2: Yeah, with BC7 LZ4 only compresses it down to 4.6MiB.
>PS I think that BC could be massaged at compression to be better compressible, and i think i read something about that. Don't remember.
There's Oodle BC7Prep from RAD Game Tools: http://www.radgametools.com/oodletexture.htm
EDIT: RAD page states that "BC7 blocks that are often very difficult to compress", so that might be also a factor why my DXT5 test compressed much better than your BC7.
EDIT2: Yeah, with BC7 LZ4 only compresses it down to 4.6MiB.