METAFONT is another macro language where everything is context sensitive because macros redefine everything. But METAFONT has a BNF grammar that describes the l

METAFONT is another macro language where everything is context sensitive because macros redefine everything. But METAFONT has a BNF grammar that describes the language after the macro expansion. Perhaps the problem with TeX are the catcodes, that redefine at runtime how every future token is interpreted even after macro expansion?