1997 Lexus ES 400 car brakes

When you say "Still doing the same thing.." are you saying you replaced the master cylinder??? If so, did you bleed it???

When you bleed your brakes, you must bleed all four wheels. And whenever you replace the master cylinder, you must bleed that also.

And you rubber brake lines could be soft (bad), causing your soft pedal. Check those by squeezing them and visually inspecting them for any "bulging". If they're soft in certain spots or there's any bulging, replace them. And it's a good idea to replace them as a set.