What isn't good is hitting the first man time and time again. It's a cardinal sin in football.
It really isn't a cardinal sin. Its a consequence of trying to deliver a good corner. One that is played with pace and stays flat. Ideally, you need your corner to miss the first man by a couple of inches, but by trying to do that you're going to bring him into play more often.
The alternative is just to float a corner into the middle of the box or towards the back post, which not only gives the defenders a massive advantage, it also means its more likely that the 'keeper can come and claim it. Even if an attacking player gets to it, the lack of pace on the ball makes it much more difficult to score as they will need to generate the pace themselves. Or they will be too far out to do anything.
In short, I dislike anyone who trots out the cliche around not beating the first man from a set-piece. Any footballer in the World could do it if they tried. But they aren't putting in a corner with the aim of beating the first man, they're putting in a corner with the aim of providing the best possible chance to score.