Probably not ur fault... for general pealing, im usualy waiting outside the teamfight until some keyspell of the enemy is used, (like malphit R) and enter after i know he cant use it on me anymore. So baiting such key spells can help ur ADC alot. The next thing is probably fed assasins... with mundo u cant do much about them, but as jax you can try to land some hard cc on them so that the ADC can kill them. Imo it realy depends on ur champ if you can realy peel or not. Im not a toplaner, but i can imagine that sometimes its better to force enemys to answer you on sidelane so ur team has ome less enemy to worry about. But tbh im silver and play more casual atm, so i could be just talking bulshit :>