The swirly background (especially on the main screen), shiny card effects, and the CRT distortion effect would be genuinely difficult to implement on a system from that era. Balatro does all three with a couple hundred lines of GLSL shaders.

(The third would, of course, be redundant if you were actually developing for a period 486. But I digress.)

Some fans ported Balatro to the VBA if you want a comparison of what is possible.

But the buffer for a full HD screen fill most of the memory of a typical 486 computer I think

Virtually all the graphics? Modern computers are very fast.