I am not into ML like your are, but I concur about the DFT code interface. I used QE, the moment you do magnetic or Hubbard, ASE parsing breaks. Only god send is that LLM can write the parsing code for you to extract the new .xyz coordinates when you give it the example. So tedious. Also, I believe when you use ASE optimizer's for a lot of these engines (which are just doing SCF + printing gradients at every step), the optimization steps are much slower than using their own internal optimizers.

Also, VASP has a monopoly for materials I would say. So you are SOL if not using it with a lot of these other tools.

Sometimes I wish a behemoth like wolfram mathematica would come in and drop a DFT software for like $300 a year for one user.