Cleaning this old horrible bathroom floor! I’ve tried everything

https://www.doityourself.com/stry/how-to-paint-ceramic-tile-flooring

Try Bon Ami. This will be tedious, but may work without damaging the surface areas. Bar Keeper's friend works on Porcelain, but contains oxalic acid, so follow instructions, to the letter

Paint or get self stick tiles and put them over top. Make sure you do not have too many layers or it may keep door from closing and may be a safety hazard.

I would clean it with TSP then paint it. Here is an example...you could stencil it or leave it plain.

https://www.hometalk.com/diy/paint/i-painted-and-stenciled-my-ceramic-tile-30107044?r=2

You can try out these other cleaning solutions! Hope it helps, Good luck!

https://www.hometalk.com/categories/clean/floors/tiles

Obviously, you can’t do anything until the grout is clean anyway, so consider, when it’s clean, updating the grout with gray.

Its obviously really kind of funky. Some would love its retro-chic.

Have you tried Mr Clean magic sponges? Or a bunch of Dollar store fakes. Mr Cleans cleaned my tub when 10 years of other stuff wouldn’t. Rinse well.

Best of luck.

I would buy peel and stick tiles and put them over top. I don't think these can be cleaned--- the surface has probably been scratched from repeated cleanings. Just make sure you rough up the surface before placing the new tiles down for better adhesion.