A good broadhead through both lungs will kill a deer very fast and humanely. My largest deer was killed at 9 yards and ran 30 yards before collapsing. As fast as deer run, that is less than 5 seconds. My string was barely done vibrating when I heard it collapse.
If you can't get the arrow where it needs to be, then no, it won't kill the deer very well at all. Bowhunting requires dedication and restraint. For me bowhunting involves practicing throughout the year, almost a lifestyle. My maximum hunting range is the range at which I can be almost certain of making a clean kill. That might be 7 yards or 30, or zero. There are many times in bowhunting where you just don't have a shot. Wishing you did won't change that. I personally don't think anyone has any business shooting at deer past 35 yards with a bow.
Equipment in archery is a very personal thing and only practice and dedication will get you where you need to be with it. I like a fairly long bow, 55lb, medium letoff, caliper release with a string loop, custom string peep sight, a single pin adjustable site with the carbon fiber pin removed (yes REMOVED), carbon arrows heavy enough to get me down (yes, DOWN) to ~250 fps, 3, 4" real turkey feathers in a bright color with full helical fletching, and nothing else but muzzy broadheads. when I was hunting I could shoot pie plate groups at 50 yards but would never shoot at a deer past 25.
Due to an immature fixation on power and pride, the majority of bowhunters have bows that are too heavy for them. You should be able to hold you hunting bow back for minutes. Not seconds. And you should be able to draw it in an awkward position wearing odd clothing and after having sat still for hours. Be honest with yourself. I can draw a 65 pound bow smoothly in the bow shop.
My current lifestyle no longer permits me the time to keep my skills and body and equipment in shape, so even though I have the time to bowhunt, I really don't.
Crossbow hunting offers some of the same up close action and excitement of bowhunting without the time investment.