The got tomb raider one demake running on a GBA recently.
Anything is possible
The N64 can barely run Quake for PC. And SCummVM.
The GBA doesn't have any 3D graphics hardware, yet it renders that Tomb Raider game with 3D graphics in real time using a software rasterizer, on a CPU with half the clock rate of the CPU in the PS1 and with a fraction of the RAM of a PS1. So no, this is not "just a tiny step down from a PSX".