There are no exact guides to actually get better especially when trying to climb through ranked matches. Everything will depend on the player's skill level and even team dynamics. However, sometimes it could definitely help to check what makes each tier different from the rest. Checking the most used heroes for every tier could make players realize a thing or two.
"Overwatch" game director Jeff Kaplan posted on the forums just recently showing the top ten most-played heroes for each of the skill tiers, at least as of right now with season 9 just beginning. It may take a while to discuss each tier and the possible reasons for the top-played heroes.
However, what is common in almost all of the tiers is that D.Va is the number one most-played except in Platinum and Diamond tiers in which she still remains second. When it comes to playing tanks, Reinhardt is the usual choice for players in the Bronze up to Platinum tiers. Above Platinum, Roadhog is the choice for the more professional players.
As for the damage-based champions, it would either be Junkrat or Soldier: 76 who are commonly seen in the lower-skill tiers up to Platinum. Above Platinum, players usually use Genji, McCree and Tracer.
Speaking of Genji and Tracer, two heroes that would undoubtedly need skill to be used properly, Genji appears in all tiers but mostly on higher-level ones while Tracer is the highest, behind D.Va, only in Grandmaster as she falls at the lower half on Master and Diamond.
As for what this all means, it could be all up to the player's interpretation of the character that they can try out in the game. There are discussions of it as well on Kaplan's post from the users who are more engaged in the game.
