I just ordered a custom steel bike with a carbon fork which will be ready in 5-6 months. My current bike is all steel.

Any carbon tube on your bike frame that gets hit in a collision can easily be compromised to the point where it needs replacing. Bent/dented carbon cracks and becomes useless. Bent/dented steel tubes can more easily be repaired. An all carbon bike will usually not fair as well in a collision as a steel bike.

That said, carbon bikes are way lighter and will be easier to go fast. A steel bike can get you up the steepest hills, though, if you have wide range gearing. Steel is really comfy over long distances.
I think overall a steel bike will outlast a carbon bike by many years. But if speed is your goal then all carbon is a good choice. It *is* often more expensive than steel bikes.

Because most people are looking for speed when they choose carbon, most pre-made carbon bikes are made in an aggressive racing geometry- not as comfy for long mileage or touring. Notice how you don't see carbon touring bikes on the market. I'm not sure how or to what extent they can make "custom" carbon bikes or if they make them with relaxed geometry.
Steel is easier to make a custom bike fit exactly to your particular body proportions and measurements and your desired posture. Also, steel bikes already come in many geometries: racing, touring, hybrid, etc.

Aside from all this....If you like riding on rough gravel back country roads, you will want a bike that can take something a bit wider/sturdier than 23mm racing tires. Wider tires will also give you a smoother ride. I ride 770 x 28c tires on my steel bike and I ride really rough gravel roads sometimes, even on cow pasture paths, with no flats.