Hitting a limit of exponential expansion in computing is akin to hitting a speed-of-light limit in velocity: you cannot go faster than the speed of light because your mass divides by zero causing energy to multiply by infinity. The arguments against are akin to "yeah, but what if there's another universe where going faster than the speed of light doesn't make your mass divide by zero?"
Okay, fine. But your simulating universe no longer has relativity as we understand it. Fundamental shit like how protons and electrons interact has changed. "matter" means something different there. Prior to this paper the navel-staring eggheads were all "well what if it's all, like, a simulation, maaaan?" and the argument made by the paper is "if it's a simulation it's running somewhere so unlike our universe that now you're just trying to dig out a new definition of God."