You'll always have more leverage from the drops, but you should be able to brake effectively from the hoods.

What concerns me is that you're okay with the right brake, but not with the left. What's the difference? Are they not installed in the same place on the bars? Is the left one sticking? When you're not on the bike and you squeeze the brake levers, does the left one take more force to squeeze than the right one? Or, do you have an injury on the left side that gives you weakness?

If they've got the levers set up crooked, or if the left (front) brake isn't working properly, that's a problem and they should fix it immediately with no charge to you.