Unfortunately public transportation can be miserable. Homeless will ruin the experience (see how Paris metro and bus stops often smell). It can be dirty, smelly, congested, unreliable, taken hostage by unions that demand unjustified never-ending benefits, not well available outside densely populated areas (even though you pay for it in tax), time consuming (connecting several trains buses back to back in a day), you may share with lots of crazies, etc.

I wasted a lot of time and got burned out in the public transportation system.

But the experience was better in some cities, eg, in German ones.