Hawk Diesel
Adventurer
Well, if you take the Repelling Blast Cantrip, this is only a problem for your first beam (unless it misses). It’s still a good idea to have a melee Cantrip in your back pocket, but often it’s worth the disadvantage on the first attack to get the following ones off.
That's fair, but unless you have an ally with Sentinel or Polearm Master, there's nothing stopping that enemy from running right back in the Warlock's face, especially if they move faster than 30ft. Also, this assumes there's room. Tight corridors, pit traps, fighting in water... all things that may negate the benefit of Repelling Blast.