Looking for advice

I'm hardstuck. Literally hardstuck, as much as I know I just have to improve to climb out, I can't. I fell from s1 to s5, and now I can't even get to s4. I went back to my best champions, I narrowed my pool, i focused on cs, died less, traded smarter, and placed more wards, but as well as I do early game, I cant seem to win. The only way I can ever win is if either my mid or my adc gets fed. That is my win condition. I play mostly tanks or cc fighters, and I try to roam and gank to the best of my ability, but nothing ever seems to help put my team ahead.

Typically what happens is I do well in lane, I try to roam, realize the enemy laner is much stronger than mine, die once. Okay, I go back to farm more, maybe get another kill or so on my laner, mid game hits, and holy shit the enemy team is so much stronger and better coordinated.

I don't know what to do. If it keeps happening to me consistently then there must be something I'm not doing right, but I cant figure out what it is. I don't believe its just pure luck of the draw that my adc or mid doesnt feed theirs. There has to be something. Please help, if you can.

thanks.