Whenever I see "bare-metal" thrown around, I think about how Atari Pong was literally all hardware, as in the entire game was printed on the circuit board as actual physical logic gates. With the advancements of modern technology, I wonder if it's possible to put something much more complex yet completely functional as a standalone program on a circuit board.
The "easy" way is a configurable logic device like an FPGA or PLD. But that's still a programming effort more than logic circuit design.
Modern discrete logic chips can be tiny. A cursory browse through Digikey shows some single NAND gates in a 1x1.5mm package. You can probably get smaller if you want, but that's still ridiculously tiny.
Given that and the insane accuracy of modern PCB printing and pick and place machine assembly, you can design a very complex circuit in an extremely small footprint.
From there, the hard part is designing the logic. Today, you'd probably use something similar to an FPGA compiler that turns a program into a logic circuit. Which leaves the hardest part as laying out the circuit on the board.
So yes, you could do it and do it extremely small. But there's good reasons this isn't generally done anymore.
https://i.redd.it/kxks306cu9y81.jpg