dijitso is part of legacy FEniCS. The python layer of dolfinx does not use dijitso, instead it uses CFFI. And the default cache directory is the one you’ve referred to.
Regarding many files in your cache. Make sure you’re properly generating dolfinx.fem.form objects outside of for/while loops. See, e.g., Speeding up time-dependent diffusion equation - #6 by nate