Not to put too fine a point on it, but this is one of those questions that if you have to ask, you need a lot more information than you realize.
I'll give it a shot.
The problem here is not the caliber, but the choice of the bullet. And not the bullet weight, but the strength of the bullet's construction. Some bullets are intended for small varmints and will expand so quickly that they essentially disintegrate in a prairie dog sized critter. These are likely to "blow up" before they penetrate deeply enough to reach the vitals, causing only a disabling wound but allowing the deer to escape. Others will not expand at all. What you would want is a bullet that will begin to expand after penetrating 6-8 inches and then stay intact to penetrate deep enough to pass through the other side of a deer sized animal.
Most bullets in the heavier range for a caliber are constructed more heavily than the lighter ones. But not always. You will need to research your bullet on the manufacturer's website, online, calling the manufacturer, or possibly online. Check several places for consistency.
Don't just pick a heavy bullet. You could end up with a VLD boat tail hollow point intended for shooting targets at 800-1000 yards. These will not reliably expand, and they are not even tested for expansion, even though they are in the 70-90gr range, heavy for the caliber. Nor are they likely to be accurate for you, unless your barrel is rifled with a fast 6-7" twist.
It is within the realm of acceptably ethical hunting practice to use a .223 for hunting whitetail deer if you use a proper bullet and select your shots.
But if you're not going to properly research and find a proper bullet, the answer is "No, the .223 is not suitable for hunting deer sized game."