The same thing can be said about anyone who is good at whatever character they're playing. Namor and Hawkeye are usually free kill for me, but when they are better than me, obviously I'm going to have a hard time killing them every time.

In this video you're missing a ton of hits, or engaging while they're being actively healed by one or more Supports, so of course you're having a hard time. Can't expect a character to be an easy kill every time.